0001193125-21-121875 | 20-F | XBRL Viewer

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Cover Page	12 Months Ended
Cover Page	Dec. 31, 2020 shares
Document Information [Line Items]
Document Type	20-F
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Registrant Name	ChipMOS TECHNOLOGIES INC.
Entity Central Index Key	0001123134
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	727,240,126
Document Annual Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes
Document Shell Company Report	false
Entity Incorporation, State or Country Code	F5
Document Accounting Standard	International Financial Reporting Standards
Entity Voluntary Filers	No
Entity Address, Country	TW
ICFR Auditor Attestation Flag	true
ADR [member]
Document Information [Line Items]
Trading Symbol	IMOS
Title of 12(b) Security	American Depositary Shares
Security Exchange Name	NASDAQ
Ordinary shares [member]
Document Information [Line Items]
Title of 12(b) Security	Common Shares, par value NT$10 per share
No Trading Symbol Flag	true
Security Exchange Name	NASDAQ

Consolidated Statements of Financial Position $ in Thousands, $ in Thousands	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)
Current assets
Cash and cash equivalents	$ 4,113,651	$ 146,498	$ 4,704,084
Current financial assets at fair value through profit or loss	53,120	1,892
Current financial assets at amortized cost	206,482	7,353	168,970
Current contract assets	389,016	13,854	377,869
Notes receivable, net	599	21	765
Accounts receivable, net	5,364,156	191,031	4,452,904
Accounts receivable – related parties			1,045
Other receivables	51,436	1,832	89,676
Other receivables – related parties			2,948
Current tax assets			138,941
Inventories	2,102,075	74,860	1,767,642
Prepayments	75,568	2,691	57,502
Total current assets	12,356,103	440,032	11,762,346
Non-current assets
Non-current financial assets at fair value through profit or loss	10,368	369	11,038
Non-current financial assets at fair value through other comprehensive income	262,007	9,331	121,808
Non-current financial assets at amortized cost	48,319	1,721	68,450
Investments accounted for using equity method	3,271,677	116,513	3,392,910
Property, plant and equipment, net	17,994,686	640,836	17,979,444
Right-of-use assets	859,069	30,594	687,068
Deferred tax assets	185,691	6,613	194,552
Refundable deposits	21,186	754	21,145
Other non-current assets	71,708	2,554	67,126
Total non-current assets	22,724,711	809,285	22,543,541
Total assets	35,080,814	1,249,317	34,305,887
Current liabilities
Current contract liabilities			1,231
Notes payable	2,899	103
Accounts payable	966,821	34,431	819,548
Other payables	3,249,403	115,719	2,977,036
Current tax liabilities	580,430	20,671	386,832
Current provisions	3,463	123	1,998
Current lease liabilities	132,549	4,721	24,567
Receipts in advance	10,790	384	988
Long-term bank loans, current portion	748,353	26,651	748,419
Current refund liabilities	9,864	351	26,000
Other current liabilities	21,059	750	32,242
Total current liabilities	5,725,631	203,904	5,018,861
Non-current liabilities
Long-term bank loans	6,985,212	248,761	8,293,226
Deferred tax liabilities	310,427	11,055	309,129
Non-current lease liabilities	737,946	26,280	668,384
Long-term deferred revenue	72,438	2,580
Net defined benefit liability, non-current	511,651	18,221	480,107
Guarantee deposits	21,670	772	1,095
Other non-current liabilities			4,500
Total non-current liabilities	8,639,344	307,669	9,756,441
Total liabilities	14,364,975	511,573	14,775,302
Equity attributable to equity holders of the Company
Capital stock	7,272,401	258,989	7,272,401
Capital surplus	6,050,787	215,484	6,050,787
Retained earnings
Legal reserve	1,837,894	65,452	1,579,478
Special reserve	19,802	705
Unappropriated retained earnings	5,401,569	192,364	4,651,215
Other equity interest
Financial statements translation differences of foreign operations	(61,330)	(2,184)	(89,682)
Unrealized gain on valuation of financial assets at fair value through other comprehensive income	194,716	6,934	66,386
Total equity	20,715,839	737,744	19,530,585
Total liabilities and equity	$ 35,080,814	$ 1,249,317	$ 34,305,887

Consolidated Statements of Comprehensive Income $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($) $ / shares	Dec. 31, 2020 USD ($) $ / shares	Dec. 31, 2019 TWD ($) $ / shares	Dec. 31, 2018 TWD ($) $ / shares
Statement [LineItems]
Revenue	$ 23,011,381	$ 819,493	$ 20,337,881	$ 18,480,027
Cost of revenue	(17,979,208)	(640,285)	(16,411,742)	(15,050,032)
Gross profit	5,032,173	179,208	3,926,139	3,429,995
Sales and marketing expenses	(56,978)	(2,029)	(56,076)	(53,451)
General and administrative expenses	(528,759)	(18,830)	(498,241)	(485,068)
Research and development expenses	(1,015,512)	(36,165)	(1,007,631)	(939,269)
Other income (expenses), net	135,578	4,828	92,928	147,514
Operating profit	3,566,502	127,012	2,457,119	2,099,721
Interest income	27,778	989	64,368	49,971
Other income	21,157	753	10,759	8,390
Other gains and losses	(323,267)	(11,512)	(148,414)	114,709
Finance costs	(171,482)	(6,107)	(180,262)	(190,248)
Share of loss of associates and joint ventures accounted for using equity method	(147,329)	(5,247)	(154,926)	(300,101)
Gain on disposal of investment accounted for using equity method			973,609
Profit before income tax	2,973,359	105,888	3,022,253	1,782,442
Income tax expense	(594,381)	(21,167)	(513,679)	(456,618)
Profit for the year	2,378,978	84,721	2,508,574	1,325,824
Other comprehensive income (loss):
(Loss) profit on remeasurements of defined benefit plans	(51,990)	(1,851)	20,916	(59,961)
Unrealized gain (loss) on valuation of equity instruments at fair value through other comprehensive income	140,199	4,993	(52,549)	85,022
Share of other comprehensive (loss) income of associates and joint ventures accounted for using equity method that will not be reclassified to profit or loss	23,143	824	5,732	(2,687)
Income tax effect on components that will not be reclassified to profit or loss	(24,396)	(869)	2,833	(4,126)
Net other comprehensive income (loss) that will not be reclassified to profit or loss in subsequent periods	86,956	3,097	(23,068)	18,248
Exchange differences on translation of foreign operations	28,352	1,010	(104,198)	(51,077)
Net other comprehensive (loss) income that will be reclassified to profit or loss in subsequent periods	28,352	1,010	(104,198)	(51,077)
Other comprehensive (loss) income for the year, net of income tax	115,308	4,107	(127,266)	(32,829)
Total comprehensive income for the year, net of income tax	$ 2,494,286	$ 88,828	$ 2,381,308	$ 1,292,995
Ordinary shares [member]
Other comprehensive income (loss):
Earnings per share — basic \| (per share)	$ 3.27	$ 0.12	$ 3.45	$ 1.65
Earnings per share — diluted \| (per share)	3.23	0.11	3.40	1.63
American depositary share (each representing 20 common shares) [member]
Other comprehensive income (loss):
Earnings per share — basic \| (per share)	65.42	2.33	69.00	33.03
Earnings per share — diluted \| (per share)	$ 64.57	$ 2.30	$ 68.06	$ 32.59

Consolidated Statements of Changes in Equity $ in Thousands, $ in Thousands	TWD ($)	USD ($)	Capital stock [member] TWD ($)	Capital surplus [member] TWD ($)	Legal reserve [member] TWD ($)	Special reserve [member] TWD ($)	Unappropriated retained earnings [member] TWD ($)	Financial statements translation differences of foreign operations [member] TWD ($)	Unearned employee awards [member] TWD ($)	Treasury stock [member] TWD ($)	unrealized gain (loss) on valuation of financial assets at fair value through other comprehensive income [member] TWD ($)	Unrealized gain (loss) on valuation of available -for-sale financial assets [member] TWD ($)
Beginning Balance (Previously stated [member]) at Dec. 31, 2017	$ 18,120,949		$ 8,862,971	$ 6,271,448	$ 1,166,517		$ 2,815,966	$ 65,593	$ (54,570)	$ (1,007,654)		$ 678
Beginning Balance (Increase (decrease) due to changes in accounting policy required by IFRSs [member]) at Dec. 31, 2017	107,215						65,050				$ 42,843	$ (678)
Beginning Balance (Restated balance [member]) at Dec. 31, 2017	18,228,164		8,862,971	6,271,448	1,166,517		2,881,016	65,593	(54,570)	(1,007,654)	42,843
Profit for the year	1,325,824						1,325,824
Other comprehensive (loss) income	(32,829)						(45,807)	(51,077)			64,055
Total comprehensive income (loss) for the year (Note 23)	1,292,995						1,280,017	(51,077)			64,055
Appropriation of prior year's earnings:
Legal reserve (Note 22)					302,653		(302,653)
Cash dividends (Note 22)	(256,806)						(256,806)
Restricted shares (Note 19)	41,043		(4,948)	(7,967)			1,089		52,869
Capital reduction	(1,284,223)		(1,329,446)	72						45,151
Ending Balance at Dec. 31, 2018	18,021,173		7,528,577	6,263,553	1,469,170		3,602,663	14,516	(1,701)	(962,503)	106,898
Profit for the year	2,508,574						2,508,574
Other comprehensive (loss) income	(127,266)						17,372	(104,198)			(40,440)
Total comprehensive income (loss) for the year (Note 23)	2,381,308						2,525,946	(104,198)			(40,440)
Appropriation of prior year's earnings:
Legal reserve (Note 22)					110,308		(110,308)
Cash dividends (Note 22)	(872,718)						(872,718)
Restricted shares (Note 19)	822		(477)	(412)			10		$ 1,701
Cancellation of treasury stock (Note 20)			(255,699)	(212,354)			(494,450)			$ 962,503
Disposal of investment accounted for using equity method (Note 23)							72				(72)
Ending Balance at Dec. 31, 2019	19,530,585		7,272,401	6,050,787	1,579,478		4,651,215	(89,682)			66,386
Profit for the year	2,378,978	$ 84,721					2,378,978
Other comprehensive (loss) income	115,308	4,107					(41,374)	28,352			128,330
Total comprehensive income (loss) for the year (Note 23)	2,494,286	88,828					2,337,604	28,352			128,330
Appropriation of prior year's earnings:
Legal reserve (Note 22)					258,416		(258,416)
Special reserve (Note 22)						$ 19,802	(19,802)
Cash dividends (Note 22)	(1,309,032)						(1,309,032)
Ending Balance at Dec. 31, 2020	$ 20,715,839	$ 737,744	$ 7,272,401	$ 6,050,787	$ 1,837,894	$ 19,802	$ 5,401,569	$ (61,330)			$ 194,716

Consolidated Statements of Cash Flows $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Cash flows from operating activities
Profit before income tax	$ 2,973,359	$ 105,888	$ 3,022,253	$ 1,782,442
Adjustments to reconcile profit (loss)
Depreciation expenses	4,175,519	148,701	3,731,914	3,376,579
Expected (reversal of) credit losses	264	10	(806)	348
Interest expense	162,400	5,783	171,075	152,416
Interest income	(27,778)	(989)	(64,368)	(49,971)
Dividend income	(3,229)	(115)	(585)	(571)
Share-based payments			822	41,043
Share of loss of associates and joint ventures accounted for using equity method	147,329	5,247	154,926	300,101
Gain on valuation of financial assets at fair value through profit or loss	(24,015)	(855)	(1,317)	(1,485)
Gain on disposal of property, plant and equipment, net	(48,070)	(1,712)	(20,271)	(14,274)
Insurance compensation income			(10,435)	(147)
Impairment loss on property, plant and equipment			9,938
Gain on disposal of investment accounted for using equity method			(973,609)
Deferred revenue	(10,143)	(361)	(12,279)	(42,857)
Financial assets at fair value through profit or loss	(28,435)	(1,013)	1,750	1,447
Current contract assets	(11,150)	(397)	(78,013)	(44,858)
Accounts and notes receivable	(911,355)	(32,456)	294,409	(733,695)
Accounts receivable – related parties	1,045	37	(905)	(129)
Other receivables	13,529	482	(8,082)	5,238
Other receivables – related parties	4,923	175	12,437	16,317
Inventories	(334,433)	(11,910)	11,193	(58,101)
Prepayments	(10,485)	(373)	(4,333)	46,781
Other non-current assets	6,337	226	6,914	6,914
Current contract liabilities	(1,231)	(44)	(201)	280
Accounts and notes payable	170,172	6,060	182,277	(50,689)
Accounts payable – related parties			(347)	121
Other payables	112,151	3,994	331,207	(301,711)
Other payables – related parties			(218)	182
Current provisions	1,465	52	(27,354)	(27,803)
Current refund liabilities	(16,136)	(575)	(6,627)	(37,529)
Other current liabilities	(11,183)	(398)	1,442	(475)
Net defined benefit liability, non-current	(20,446)	(728)	(19,742)	(17,722)
Cash generated from operations	6,310,404	224,729	6,703,065	4,348,192
Interest received	32,817	1,169	67,105	48,590
Dividends received	23,229	827	20,585	6,184
Interest paid	(150,135)	(5,346)	(171,149)	(154,307)
Income tax paid	(276,079)	(9,832)	(637,169)	(119,473)
Net cash generated from operating activities	5,940,236	211,547	5,982,437	4,129,186
Cash flows from investing activities
(Increase) decrease in financial assets at amortized cost	(17,381)	(619)	30,851	(198,030)
Proceeds from insurance compensation			10,435	147
Acquisition of investments accounted for using equity method				(794,694)
Proceeds from disposal of investment accounted for using equity method			1,180,179
Acquisition of property, plant and equipment	(3,961,026)	(141,062)	(5,440,621)	(4,154,198)
Proceeds from disposal of property, plant and equipment	87,107	3,102	21,434	18,160
(Increase) decrease in refundable deposits	(41)	(1)	861	(664)
Increase in other non-current assets	(10,919)	(388)	(45,480)
Increase in long-term deferred revenue	85,909	3,059	4,500
Proceeds from capital reduction of investment in associate	17,000	605
Net cash used in investing activities	(3,799,351)	(135,304)	(4,237,841)	(5,129,279)
Cash flows from financing activities
Proceeds from short-term bank loans	151,071	5,380	834,955	1,053,202
Payments on short-term bank loans	(151,071)	(5,380)	(834,955)	(2,022,555)
Payment on lease liabilities	(84,928)	(3,024)	(48,161)
Proceeds from long-term bank loans	4,429,593	157,749		12,663,550
Payments on long-term bank loans	(5,756,450)	(205,002)	(756,450)	(12,553,300)
(Decrease) increase in guarantee deposits	575	20	3	(279)
Cash dividend paid	(1,309,032)	(46,618)	(872,718)	(256,806)
Payments on capital reduction				(1,284,223)
Net cash used in financing activities	(2,720,242)	(96,875)	(1,677,326)	(2,400,411)
Net (decrease) increase in cash and cash equivalents	(579,357)	(20,632)	67,270	(3,400,504)
Effect of foreign exchange rate changes	(11,076)	(394)	(5,708)	7,312
Cash and cash equivalents at beginning of year	4,704,084	167,524	4,642,522	8,035,714
Cash and cash equivalents at end of year	$ 4,113,651	$ 146,498	$ 4,704,084	$ 4,642,522

Corporate and group information

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Corporate and group information

1.	Corporate and group information

ChipMOS TECHNOLOGIES INC. (the “Company” or “ChipMOS Taiwan”) was incorporated in the Republic of China (“ROC”) on July 28, 1997. The Company and its subsidiaries (collectively referred herein as the “Group”) are primarily engaged in the research, development, manufacturing and sale of high-integration and high-precision integrated circuits and related assembly and testing services. On April 11, 2014, the Company’s shares were listed on the Taiwan Stock Exchange (“TWSE”). On November 1, 2016, the Company’s American Depositary Shares (“ADSs”) were listed on the NASDAQ Global Select Market and traded under the ticker symbol “IMOS”.

The authorization of the consolidated financial statements

12 Months Ended

Dec. 31, 2020

Text block [abstract]

The authorization of the consolidated financial statements

2.	The authorization of the consolidated financial statements

The accompanying consolidated financial statements were authorized for issuance by the Board of Directors on April 20, 2021.

Application of new and revised International Financial Reporting Standards ("IFRS"), International Accounting Standards ("IAS"), International Financial Reporting Interpretations Committee ("IFRIC") Interpretations and Standing Interpretations Committee ("SIC") Interpretations issued by the International Accounting Standards Board ("IASB"), (collectively, "IFRSs")

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Application of new and revised International Financial Reporting Standards (“IFRS”), International Accounting Standards (“IAS”), International Financial Reporting Interpretations Committee (“IFRIC”) Interpretations and Standing Interpretations Committee (“SIC”) Interpretations issued by the International Accounting Standards Board (“IASB”), (collectively, “IFRSs”)

Amendments to IFRSs and the new interpretation that are mandatorily effective for the current year


New Standards, Interpretations and Amendments		Effective date issued by IASB
Amendments to IAS 1 and IAS 8, “Disclosure Initiative — Definition of Material”		January 1, 2020
Amendments to IFRS 3, “Definition of a Business”		January 1, 2020
Amendments to IFRS 9, IAS 39 and IFRS 7, “Interest Rate Benchmark Reform”		January 1, 2020
Amendment to IFRS 16, “Covid-19-Related Rent Concessions”		June 1, 2020

Based on the Group’s assessment, the above standards and interpretations have no significant impact on the Group’s financial position and financial performance.

New standards, interpretations and amendments in issue but not yet effective


New Standards, Interpretations and Amendments		Effective date issued by IASB
Amendments to IFRS 4, “Extension of the Temporary Exemption from Applying IFRS 9”		January 1, 2021
Amendments to IFRS 9, IAS 39, IFRS 7, IFRS 4 and IFRS 16, “Interest Rate Benchmark Reform-Phase 2”		January 1, 2021
Amendments to IFRS 3, “Reference to the Conceptual Framework”		January 1, 2022
Amendments to IFRS 10 and IAS 28, “Sale or Contribution of Assets between an Investor and its Associate or Joint Venture”		To be determined by IASB
IFRS 17, “Insurance Contracts”		January 1, 2023
Amendments to IFRS 17, “Insurance Contracts”		January 1, 2023
Amendments to IAS 1, “Classification of Liabilities as Current or Non-current”		January 1, 2023
Amendments to IAS 1, “Disclosure of Accounting Policies”		January 1, 2023
Amendments to IAS 8, “Definition of Accounting Estimates”		January 1, 2023


New Standards, Interpretations and Amendments		Effective date issued by IASB
Amendments to IAS 16, “Property, Plant and Equipment: Proceeds before Intended Use”		January 1, 2022
Amendments to IAS 37, “Onerous Contracts—Cost of Fulfilling a Contract”		January 1, 2022
Annual Improvements to IFRS Standards 2018–2020		January 1, 2022

Based on the Group’s assessment, the above standards and interpretations have no significant impact on the Group’s financial position and financial performance.

Summary of significant accounting policies

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of significant accounting policies

4.	Summary of significant accounting policies

The significant accounting policies applied in the preparation of these accompanying consolidated financial statements are set out below. These policies have been consistently applied during the reported periods, unless otherwise stated.

Statement of compliance

The consolidated financial statements of the Group have been prepared in accordance with IFRSs as issued by the IASB.

Basis of preparation

(a)

Except for the following items, the consolidated financial statements have been prepared under the historical cost convention:

Financial assets at fair value through profit or loss (including derivative instruments).

ii)

Financial assets at fair value through other comprehensive income.

iii)

Defined benefit liabilities were recognized based on the net amount of pension fund assets less the present value of benefit obligation.

(b)

The preparation of the consolidated financial statements in conformity with IFRSs requires the use of certain critical accounting estimates. It also requires management to exercise its judgment in the process of applying the Group’s accounting policies. The areas involving a higher degree of judgment or complexity, or areas where assumptions and estimates are significant to the consolidated financial statements are disclosed in Note 4 dd).

(c)

These consolidated financial statements are presented in New Taiwan dollars (“NT$”), which is the Company’s functional currency.

(d)

The initial adoption of IFRS 16 “Lease” (“IFRS 16”) is effective on January 1, 2019. The Group has elected to apply IFRS 16 by not restating the comparative information (referred herein as the “simplified retrospective approach”). Please refer to Note 45 for details of the application of IFRS 16.

Basis of consolidation

(a)

Basis for preparation of consolidated financial statements:

All subsidiaries are included in the Group’s consolidated financial statements. Subsidiaries are all entities controlled by the Group. The Group controls an entity when the Group is exposed, or has rights, to variable returns from its involvement with the entity and has the ability to affect those returns through its power over the entity. Consolidation of subsidiaries begins from the date the Group obtains control of the subsidiaries and ceases when the Group loses control of the subsidiaries.

ii)

Transactions, balances and unrealized gains or losses on transactions between companies within the Group are eliminated. Accounting policies of subsidiaries have been adjusted where necessary to ensure consistency with the policies adopted by the Group.

iii)

Profit or loss and each component of other comprehensive income are attributed to the owners of the parent and to the

non-controlling

interests. Total comprehensive income is attributed to the owners of the parent and to the

non-controlling

interests even if this results in a deficit balance in the

non-controlling

interests.

iv)

Changes in a parent’s ownership interest in a subsidiary that do not result in the parent losing control of the subsidiary (transactions with

non-controlling

interests) are accounted for as equity transactions, i.e. transactions with owners in their capacity as owners. Any difference between the amount by which the

non-controlling

interests are adjusted and the fair value of the consideration paid or received is recognized directly in equity.

When the Group loses control of a subsidiary, the Group remeasures any investment retained in the former subsidiary at its fair value. That fair value is regarded as the fair value on initial recognition of a financial asset or the cost on initial recognition of the associate or joint venture. Any difference between fair value and carrying amount is recognized in profit or loss. All amounts previously recognized in other comprehensive income in relation to the subsidiary are reclassified to profit or loss on the same basis as would be required if the related assets or liabilities were disposed of. That is, when the Group loses control of a subsidiary, all gains or losses previously recognized in other comprehensive income in relation to the subsidiary should be reclassified from equity to profit or loss, if such gains or losses would be reclassified to profit or loss when the related assets or liabilities are disposed of.

(b)

Subsidiaries included in the consolidated financial statements:

Percentage of

Ownership (%)

December 31,

Name of investor

Name of investee

Main business

Location

2019

2020

Note

The Company

ChipMOS U.S.A., Inc.
(“ChipMOS USA”)

Marketing of semiconductors and electronic related products

San Jose, USA

100

The Company

ChipMOS
TECHNOLOGIES
(BVI) LTD.

(“ChipMOS BVI”)

Holding company

British Virgin
Islands

100

ChipMOS BVI

ChipMOS
SEMICONDUCTORS
(Shanghai) LTD.
(“ChipMOS
Shanghai”)

Marketing of semiconductors and electronic related products

Shanghai,
People’s
Republic of
China
(“PRC”)

—

100

Note

Note: In order to maintain and develop market in the PRC, the Group invested and established the subsidiary, ChipMOS Shanghai on April 8, 2020 and then included it in the consolidated financial statements.

(c)

Subsidiaries not included in the consolidated financial statements: None.

(d)

Adjustments for subsidiaries with different statements of financial position dates: Not applicable.

(e)

No significant restrictions on the ability of subsidiaries to transfer funds to parent company.

(f)

Subsidiaries that have

non-controlling

interests that are material to the Group: None.

Foreign currency translation

Items included in the financial statements of each of the Group’s entities are measured using the currency of the primary economic environment in which the entity operates (the “functional currency”). The consolidated financial statements are presented in NT$, which is the Company’s functional currency and the Group’s presentation currency.

(a)

Foreign currency transactions and balances

Foreign currency transactions are translated into the functional currency using the exchange rates on the trade date or measurement date. Therefore, foreign exchange differences resulting from the settlement of such transactions are recognized in profit or loss in the period in which they arise.

ii)

Monetary assets and liabilities denominated in foreign currencies at the period end are

re-translated

at the exchange rates prevailing at the statements of financial position date. Exchange differences arising upon

re-translation

are recognized in profit or loss on the statements of financial position date.

iii)

Non-monetary

assets and liabilities denominated in foreign currencies held at fair value through profit or loss are

re-translated

at the exchange rates prevailing at the statements of financial position date; their exchange differences are recognized in profit or loss.

Non-monetary

assets and liabilities denominated in foreign currencies held at fair value through other comprehensive income are

re-translated

at the exchange rates prevailing at the statements of financial position date; their exchange differences are recognized in other comprehensive income. However,

non-monetary

assets and liabilities denominated in foreign currencies that are not measured at fair value are translated using the historical exchange rates at the initial dates of the transactions.

iv)

All foreign exchange differences are presented in the statement of comprehensive income under “Other gains and losses” by the nature of transactions.

(b)

Translation of foreign operations

The operating results and financial position of all the group entities, associates that have different functional currency and presentation currency are translated into the presentation currency as follows:

Assets and liabilities for each statements of financial position are translated at the exchange rates prevailing at the statements of financial position date;

ii)

Income and expenses for each statement of comprehensive income are translated at average exchange rates of that period; and

iii)

All exchange differences are recognized in other comprehensive income.


	e)	Classification of current and non-current assets and liabilities

(a)

Assets that meet one of the following criteria are classified as current assets:

Assets arising from operating activities that are expected to be realized, or are intended to be sold or consumed within the normal operating cycle;

ii)

Assets held mainly for trading purposes;

iii)

Assets that are expected to be realized within 12 months from the statements of financial position date;

iv)

Cash and cash equivalents, excluding restricted cash and cash equivalents and those that are to be exchanged or used to pay off liabilities more than 12 months after the statements of financial position date.

All assets that do not meet the above criteria are classified as

non-current

assets.

(b)

Liabilities that meet one of the following criteria are classified as current liabilities:

Liabilities that are expected to be settled within the normal operating cycle;

ii)

Liabilities arising mainly from trading activities;

iii)

Liabilities that are to be settled within 12 months from the statements of financial position date;

iv)

Liabilities for which the repayment date cannot be unconditionally extended to more than 12 months after the statements of financial position date. Liabilities bearing terms that could, at the option of the counterparty, result in its settlement by the issue of equity instruments do not affect its classification.

All liabilities that do not meet the above criteria are classified as

non-current

liabilities.

Cash equivalents

Cash equivalents refer to short-term, highly liquid investments that are readily convertible to known amounts of cash and are subject to an insignificant risk of changes in value (including time deposits with less than 3 months contract period). Time deposits that meet the above definition and are held for the purpose of meeting short-term cash commitments in operations are classified as cash equivalents.

Financial assets at fair value through profit or loss

(a)

Financial assets at fair value through profit or loss are financial assets that are not measured at amortized cost or fair value through other comprehensive income.

(b)

On a regular way purchase or sale basis, financial assets at fair value through profit or loss are recognized and derecognized using settlement date accounting.

(c)

At initial recognition, the Group measures the financial assets at fair value and recognizes the transaction costs in profit or loss. The Group subsequently measures the financial assets at fair value, and recognizes the gain or loss in profit or loss.

(d)

The Group recognizes the dividend income when the right to receive such payment is confirmed, inflow of the future economic benefits associated with the dividend is probable to the Group and the amount of the dividend can be measured reliably.

Financial assets at fair value through other comprehensive income

(a)

Financial assets at fair value through other comprehensive income comprise equity instruments which are not held for trading, and for which the Group has made an irrevocable election at initial recognition to recognize changes in fair value in other comprehensive income.

(b)

On a regular way purchase or sale basis, financial assets at fair value through other comprehensive income are recognized and derecognized using settlement date accounting.

(c)

At initial recognition, the Group measures the financial assets at fair value plus transaction costs. The Group subsequently measures the financial assets at fair value.

The changes in fair value of equity instruments that were recognized in other comprehensive income are reclassified to retained earnings and are not reclassified to profit or loss following the derecognition of the investment. Dividends are recognized as income when the right to receive such payment is confirmed, inflow of the future economic benefits associated with the dividend is probable to the Group and the amount of the dividend can be measured reliably.

Financial assets at amortized cost

(a)

Financial assets at amortized cost are those that meet all of the following criteria:

The objective of the Group’s business model is achieved by collecting contractual cash flows.

ii)

The financial assets’ contractual cash flows represent solely payments of principal and interest.

(b)

The Group’s time deposits which do not fall under cash equivalents are those with a short maturity period and are measured at initial investment amount as the effect of discounting is immaterial.

Accounts and notes receivable

(a)

Accounts and notes receivable entitle the Group a legal right to receive consideration in exchange for transferred goods or rendered services.

(b)

The short-term accounts and notes receivable without bearing interest are subsequently measured at initial invoice amount as the effect of discounting is immaterial.

Impairment of financial assets

For financial assets at amortized cost, at each reporting date, the Group recognizes the impairment provision for 12 months expected credit losses if there has not been a significant increase in credit risk since initial recognition or recognizes the impairment provision for the lifetime expected credit losses if such credit risk has increased since initial recognition after taking into consideration all reasonable and verifiable information that includes forecasts. On the other hand, for accounts receivable or contract assets that do not contain a significant financing component, the Group recognizes the impairment provision for lifetime expected credit losses.

Derecognition of financial assets

The Group derecognizes a financial asset when the contractual rights to receive the cash flows from the financial asset have expired.

Inventories

Inventories are initially recorded at standard costs. Cost is determined on a weighted-average cost basis. At the end of reporting period, the differences between actual costs and standard costs were allocated to inventories and cost of revenue based on an appropriate rate. Allocation of fixed production overheads is based on the normal operating capacity of the production facilities. Costs associated with underutilized capacity are expensed in the period that the cost occurs.

Inventories are valued at the lower of cost and net realizable value. Net realizable value is the estimated selling price in the ordinary course of business less the estimated costs of completion and the estimated costs necessary to make the sale. The item by item approach is used in raw materials. The amount of any write-down of inventories to net realizable value and all losses of inventories are recognized as an expense in the period the write-down or loss occurs.

Investments accounted for using equity method – associates

(a)

Associates are all entities over which the Group has significant influence but not control. In general, it is presumed that the investor has significant influence, if an investor holds, directly or indirectly 20 percent or more of the voting power of the investee. Investments in associates are accounted for using the equity method and are initially recognized at cost.

(b)

The Group’s share of its associates’ post-acquisition profits or losses is recognized in profit or loss, and its share of post-acquisition movements in other comprehensive income is recognized in other comprehensive income. When the Group’s share of losses in an associate equals or exceeds its interests in the associate, including any other unsecured receivables, the Group does not recognize further losses, unless it has incurred legal or constructive obligations or made payments on behalf of the associate.

(c)

When changes in an associate’s equity that are not recognized in profit or loss or other comprehensive income of the associate and such changes not affecting the Group’s ownership percentage of the associate, the Group recognizes the Group’s share of change in equity of the associate in “Capital surplus” in proportion to its ownership.

(d)

Unrealized gains on transactions between the Group and its associates are eliminated to the extent of the Group’s interests in the associates. Unrealized losses are also eliminated unless the transaction provides evidence of an impairment of the asset transferred. Accounting policies of associates have been adjusted where necessary to ensure consistency with the policies adopted by the Group.

(e)

In the case where an associate issues new shares and the Group does not subscribe or proportionately acquire the new shares, which results in a change in the Group’s ownership percentage of the associate while maintaining significant influence on the associate, then the Group will treat the transaction as deemed disposal and reclassify to profit or loss the proportion of the gain or loss previously recognized in other comprehensive income relating to that reduction in ownership interest where appropriate.

(f)

When the Group disposes of its investment in an associate, if it loses significant influence on this associate, the amounts previously recognized in other comprehensive income in relation to the associate are reclassified to profit or loss, on the same basis as would be required if the relevant assets or liabilities were disposed of. If it still retains significant influence on this associate, then the amounts previously recognized in other comprehensive income in relation to the associate are reclassified to profit or loss proportionately in accordance with the aforementioned approach.

Property, plant and equipment

(a)

Property, plant and equipment are initially recorded at cost. Borrowing costs incurred during the construction period are capitalized.

(b)

Subsequent costs are included in the asset’s carrying amount or recognized as a separate asset, as appropriate, only when it is probable that future economic benefits associated with the item will flow to the Group and the cost of the item can be measured reliably. The carrying amount of the replaced part is derecognized. All other repairs and maintenance are charged to profit or loss during the financial period in which they are incurred.

(c)

Land is not depreciated. Other property, plant and equipment apply cost model and are depreciated using the straight-line method to allocate their cost over their estimated useful lives. Each part of an item of property, plant and equipment with a cost that is significant in relation to the total cost of the item must be depreciated separately.

(d)

The assets’ residual values, useful lives and depreciation methods are reviewed, and adjusted if appropriate, at each financial

year-end.

If expectations for the assets’ residual values and useful lives differ from previous estimates or the patterns of consumption of the assets’ future economic benefits embodied in the assets have changed significantly, any change is accounted for as a change in estimate under IAS 8 “Accounting Policies, Change in Accounting Estimates and Errors”, from the date of the change. The estimated useful lives of property, plant and equipment are as follows:


Buildings		5 to 51 years
Machinery and equipment		2 to 8 years
Tools		2 to 4 years
Others		2 to 6 years

Leasing arrangements (lessee)

right-of-use

assets / lease liabilities

(a)

Leases are recognized as a

right-of-use

asset and a corresponding lease liability at the date at which the leased asset is available for use by the Group. For short-term leases or leases of low value assets, lease payments are recognized as an expense on a straight-line basis over the lease term.

(b)

Lease liabilities include the net present value of the remaining lease payments at the commencement date, discounted using the incremental borrowing interest rate.

Lease payments are comprised of the following:

Fixed payments, less any lease incentives receivable;

ii)

The exercise price of a purchase option, if the lessee is reasonably certain to exercise that option.

The Group subsequently measures the lease liability at amortized cost using the interest method and recognizes interest expense over the lease term. The lease liability is remeasured and the amount of remeasurement is recognized as an adjustment to the

right-of-use

asset when there are changes in the lease term or lease payments and such changes do not arise from contract modifications.

(c)

At the commencement date, the

right-of-use

asset is stated at the amount of the initial measurement of lease liability. The

right-of-use

asset is measured subsequently using the cost model and is depreciated from the commencement date to the earlier of the end of the asset’s useful life or the end of the lease term. When the lease liability is remeasured, the amount of remeasurement is recognized as an adjustment to the

right-of-use

asset.

Impairment of

non-financial

assets

The Group assesses at each statements of financial position date the recoverable amounts of those assets where there is an indication that they are impaired. An impairment loss is recognized for the amount by which the asset’s carrying amount exceeds its recoverable amount. The recoverable amount is the higher of an asset’s fair value less costs to sell or value in use. When the circumstances or reasons for recognizing impairment loss for an asset in prior years no longer exist or diminish, the impairment loss is reversed. The increased carrying amount due to reversal should not be more than what the depreciated or amortized historical cost would have been if the impairment had not been recognized.

Loans

Loans comprise long-term and short-term bank loans. Loans are recognized initially at fair value, net of transaction costs incurred. Loans are subsequently stated at amortized cost; any difference between the proceeds (net of transaction costs) and the redemption value is recognized as interest expense in profit or loss over the period of the loans using the effective interest method.

Accounts and notes payable

(a)

Accounts payable are liabilities for purchases of raw materials, goods or services and notes payable are those resulting from operating and

non-operating

activities.

(b)

The short-term accounts and notes payable without bearing interest are subsequently measured at initial invoice amount as the effect of discounting is immaterial.

Derecognition of financial liabilities

A financial liability is derecognized when the obligation specified in the contract is either discharged or cancelled or expires.

Provisions for deficiency compensation

Provisions are recognized when the Group has a present legal or constructive obligation as a result of past events, and it is probable that an outflow of economic resources will be required to settle the obligation and the amount of the obligation can be reliably estimated. Provisions are measured at the present value of the expenditures expected to be required to settle the obligation on the statements of financial position date, which is discounted using a

pre-tax

discount rate that reflects the current market assessments of the time value of money and the risks specific to the obligation. When discounting is used, the increase in the provision arising from the passage of time is recognized as interest expense. Provisions are not recognized for future operating losses.

Employee benefits

(a)

Short-term employee benefits

Short-term employee benefits are measured at the undiscounted amount of the benefits expected to be paid in respect of service rendered by employees and should be recognized as expenses when the employees render service.

(b)

Pensions

Defined contribution plans

For defined contribution plans, the contributions are recognized as pension expenses when they are due on an accrual basis. Prepaid contributions are recognized as an asset to the extent of a cash refund or a reduction in future payments.

ii)

Defined benefit plans

Net obligation under a defined benefit plan is defined as the present value of an amount of pension benefits that employees will receive on retirement for their services with the Group in the current period or prior periods. The liability recognized in the statements of financial position in respect of defined benefit pension plans is the present value of the defined benefit obligation at the statements of financial position date less the fair value of plan assets. The net defined benefit obligation is calculated annually by independent actuaries using the projected unit credit method. The discount rate is determined by using the interest rates of government bonds that are denominated in the currency in which the benefits will be paid, and that have terms to maturity approximating to the terms of the related pension liability.

Remeasurements arising on defined benefit plans are recognized in other comprehensive income in the period in which they arise and are recorded as retained earnings.

Past service costs are recognized immediately in profit or loss.

(c)

Termination benefits

Termination benefits are employee benefits provided in exchange for the termination of employment as a result from either the Group’s decision to terminate an employee’s employment before the normal retirement date, or an employee’s decision to accept an offer of redundancy benefits in exchange for the termination of employment. The Group recognizes an expense as it can no longer withdraw an offer of termination benefits, or it recognizes related restructuring costs, whichever is earlier. Benefits that are expected to be due more than 12 months after statements of financial position date shall be discounted to their present value.

(d)

Employees’ compensation and directors’ remuneration

Employees’ compensation and directors’ remuneration are recognized as expenses and liabilities, provided that such recognition is required under legal obligation or constructive obligation and those amounts can be reliably estimated. Any difference between the resolved amounts and the subsequently actual distributed amounts is accounted for as changes in estimates. If employee compensation is paid by shares, the Company calculates the number of shares based on the closing price at the previous day of the board meeting resolution.

Employee share-based payments

Restricted shares

(a)

Restricted shares issued to employees are measured at the fair value of the equity instruments granted at the grant date, and are recognized as compensation cost over the vesting period.

(b)

For restricted shares where those shares do not restrict distribution of dividends to employees and employees are not required to return the dividends received if they resign during the vesting period, the Group recognizes the fair value of the dividends received by employees who are expected to resign during the vesting period as a compensation cost at the date the dividends were declared.

(c)

For restricted shares where employees do not need to pay to acquire those shares, if an employee resigns during the vesting period, the Group will recover and retire those shares at no cost.

Income tax

(a)

The income tax expense for the period comprises current and deferred tax. Income tax is recognized in profit or loss, except to the extent that it relates to items recognized in other comprehensive income or items recognized directly in equity, in which cases the income tax is recognized in other comprehensive income or equity.

(b)

The current income tax expense is calculated on the basis of the tax laws enacted or substantively enacted at the statements of financial position date in the countries where the Group and its subsidiaries operate and generate taxable income. Management periodically evaluates positions taken in tax returns with respect to situations in accordance with applicable tax regulations. It establishes provisions where appropriate based on the amounts expected to be paid to the tax authorities. An additional income tax is levied on the unappropriated retained earnings and is recorded as income tax expense in the year the profit generated.

(c)

Deferred tax is recognized, using the balance sheet liability method, on temporary differences arising between the tax bases of assets and liabilities and their carrying amounts in the consolidated statements of financial position. However, the deferred tax is not accounted for if it arises from initial recognition of an asset or liability in a transaction other than a business combination that at the time of the transaction affects neither accounting nor taxable profit or loss. Deferred tax is provided on temporary differences arising on investments in subsidiaries and associates, except where the timing of the reversal of the temporary difference is controlled by the Group and it is probable that the temporary difference will not reverse in the foreseeable future. Deferred tax is determined using tax rates (and laws) that have been enacted or substantially enacted at the statements of financial position date and are expected to apply when the related deferred tax asset is realized or the deferred tax liability is settled.

(d)

Deferred tax assets are recognized only to the extent that it is probable that future taxable profit will be available against which the temporary differences can be utilized. At each statements of financial position date, unrecognized and recognized deferred tax assets are reassessed.

(e)

A deferred tax asset shall be recognized for the carryforward of unused tax credits resulting from equity investments to the extent that it is possible that future taxable profit will be available against which the unused tax credits can be utilized.

(f)

If a change in tax rate is enacted or substantively enacted, the Group recognizes the effect of the change immediately in the period in which the change occurs. The effect of the change on items recognized outside profit or loss is recognized in other comprehensive income or equity while the effect of the change on items recognized in profit or loss is recognized in profit or loss.

Capital stock

(a)

Ordinary shares are classified as equity. Incremental costs directly attributable to the issue of new shares in net proceeds of tax are shown in equity as a deduction.

(b)

Where the Company repurchases the Company’s shares that have been issued, the consideration paid, including any directly attributable incremental costs (net of income taxes) is deducted from equity attributable to the Company’s equity holders. Where such shares are subsequently reissued, the difference between their book value and any consideration received, net of any directly attributable incremental transaction costs and the related income tax effects, is included in equity attributable to the Company’s equity holders.

Dividends

Dividends are recorded in the Company’s financial statements in the period in which they are resolved by the Company’s shareholders. Cash dividends are recorded as liabilities; stock dividends are recorded as stock dividends to be distributed and are reclassified to ordinary shares on the effective date of new shares issuance.

aa)

Revenue recognition

(a)

The Group is primarily engaged in the customized assembly and testing services of high-integration and high-precision integrated circuits based on customer’s specification demand to create or enhance the product. When providing assembly and testing services, the Group considers:

Customer controls the provided raw materials and the Group receives the instruction from the customer on providing assembly and testing services and subsequent treatments.

ii)

The Group provides assembly and testing services to create or enhance an asset which is solely provided and controlled by the customer. The Group has no right to transfer the asset for another use.

As the asset ownership belongs to the customer, who bears the significant risk and rewards and rights on the use of the asset, the Group recognizes assembly and testing service revenue based on the progress towards completion of performance obligation during the service period.

(b)

The progress towards completion on assembly services, services for Liquid Crystal Display and other Flat-Panel Display Driver Semiconductors (“LCDD”) and Bumping are measured by the actual input costs relative to estimate total expected input costs. The progress towards completion on testing services is measured by the actual incurred testing volume. The Group provides assembly and testing services based on customer’s specification, thus, the input costs incurred to assembly and testing volume completed in testing services are not linear over the duration of these services. Customer payment on assembly and testing services is based on predetermined payment schedule. A contract asset is recognized when the Group provides services in excess of customer’s payment.

bb)

Government grants

Government grants are recognized at their fair value only when there is reasonable assurance that the Group will comply with any conditions attached to the grants will be received. Government grants are recognized in profit or loss on a systematic basis over the periods in which the Group recognizes expenses for the related costs for which the grants are intended to compensate. Government grants related to property, plant and equipment are recognized as

non-current

liabilities and are amortized to profit or loss over the estimated useful lives of the related assets using straight-line method.

cc)

Operating segments

Operating segments are reported in a manner consistent with the internal reporting provided to the chief operating decision maker. The Group’s chief operating decision maker, who is responsible for allocating resources and assessing performance of the operating segments, has been identified as the Chairman of the Board of Directors that makes strategic decisions.

dd)

Critical accounting judgments, estimates and key sources of assumption uncertainty

The preparation of the accompanying consolidated financial statements requires management to make critical judgments in applying the Group’s accounting policies and make critical assumptions and estimates concerning future events. Assumptions and estimates may differ from the actual results and are continually evaluated and adjusted based on historical experience and other factors. Such assumptions and estimates have a significant risk of causing a material adjustment to the carrying amounts of assets and liabilities within the next financial year; and the related information is addressed below:

Critical accounting estimates and assumptions

—

Revenue recognition

The Group recognizes revenue from services for assembly, LCDD and Bumping based on the progress towards completion of performance obligation during the service period. The Group estimates total expected input costs based on historical experience and measures the progress towards completion by the actual input costs relative to the total expected input costs.

Translation into U.S. dollar amounts

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Translation into U.S. dollar amounts

5.	Translation into U.S. dollar amounts

The Company maintains its accounts and expresses its consolidated financial statements in New Taiwan dollars. For convenience purposes, U.S. dollar amounts presented in the accompanying consolidated financial statements have been translated from New Taiwan dollars to U.S. dollars at the noon buying rate in the City of New York for cable transfers as certified for customs purposes by the Federal Reserve Bank of New York as of December 31, 2020, which was NT$28.08 to US$1.00. These convenience translations should not be construed as representations that the New Taiwan dollar amounts have been, or could in the future be, converted into U.S. dollars at this or any other rate of exchange.

Cash and cash equivalents

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Cash and cash equivalents

6.	Cash and cash equivalents


	December 31, 2019		December 31, 2020
	NT$000		NT$000
Cash on hand and petty cash		470		470
Checking accounts and demand deposits		915,134		2,609,421
Time deposits		3,788,480		1,503,760

		4,704,084		4,113,651

The Group transacts with a variety of financial institutions all with high credit quality to disperse credit risk, so it expects that the probability of counterparty default is remote.

No cash and cash equivalents of the Group were pledged to others.

Financial assets at fair value through profit or loss

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Financial assets at fair value through profit or loss

7.	Financial assets at fair value through profit or loss


	December 31, 2019		December 31, 2020
	NT$000		NT$000
Current:
Financial assets mandatorily measured at fair value through profit or loss
Listed stocks		—		46,512
Valuation adjustment		—		6,608

		—		53,120

Non-current:
Financial assets mandatorily measured at fair value through profit or loss
Foreign partnership interests		10,940		10,940
Valuation adjustment		98		(572	)

		11,038		10,368

Amounts recognized in profit or loss in relation to the financial assets at fair value through profit or loss are listed below:


	Year ended December 31,
	2018		2019			2020
	NT$000		NT$000			NT$000
Financial assets mandatorily measured at fair value through profit or loss
Beneficiary certificates*		1,396		1,750			18,077
Listed stocks		—		—			6,608
Foreign partnership interests		38		(433	)		(670	)
Derivative instruments		51		—			—

		1,485		1,317			24,015

Beneficiary certificates represent money market funds the Company held during the reporting period. As of December 31, 2019 and 2020, there were no beneficiary certificates classified as current financial assets at fair value through profit or loss (“FVTPL”).

No financial assets at FVTPL were pledged to others.

Information relating to price risk of financial assets at FVTPL is provided in Note 42.

Financial assets at amortized cost

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Financial assets at amortized cost

8.	Financial assets at amortized cost


	December 31, 2019		December 31, 2020
	NT$000		NT$000
Current:
Time deposits		168,970		206,482

Non-current:
Restricted bank deposits		68,450		48,319

Amounts recognized in profit or loss in relation to financial assets at amortized cost are listed below:


	Year ended December 31,
	2018		2019		2020
	NT$000		NT$000		NT$000
Interest income		920		4,467		2,206

Without taking into account any collateral held or other credit enhancements, the maximum exposure to credit risk in respect of the amount that best represents the financial assets at amortized cost held by the Group is the carrying amount at the end of each reporting period.

Information about the financial assets at amortized cost that were pledged to others as collateral is provided in Note 37.

Information relating to credit risk of financial assets at amortized cost is provided in Note 42.

Accounts receivable

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Accounts receivable

9.	Accounts receivable


	December 31, 2019			December 31, 2020
	NT$000			NT$000
Accounts receivable		4,454,255			5,365,776
Less: Loss allowance		(1,351	)		(1,620	)

		4,452,904			5,364,156

The Group’s credit term granted to customers is 30~90 days. Receivables do not bear interest. The loss allowance is determined based on the credit quality of customers. Information relating to credit risk is provided in Note 42.

The aging analysis of accounts receivable based on past due date are as follows:


	December 31, 2019		December 31, 2020
	NT$000		NT$000
Current		4,440,081		5,272,208
Within 1 month		13,733		93,568
1 – 2 months		441		—

		4,454,255		5,365,776

As of December 31, 2019 and 2020, accounts receivable were all from contracts with customers. And as of January 1, 2019, the balance of accounts receivable from contracts with customers was NT$4,745,693 thousand.

Without taking into account of any collateral held or other credit enhancements, the amount that best reflects the Group’s maximum exposure to credit risk in respect of the accounts receivable is the carrying amount at the end of each reporting period.

No accounts receivable of the Group were pledged to others.

Inventories

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Inventories

10.	Inventories

December 31, 2019

Cost

Allowance for
impairment losses

Carrying amount

NT$000

Raw materials

1,831,140

(63,498

)

1,767,642

December 31, 2020

Cost

Allowance for
impairment losses

Carrying amount

NT$000

Raw materials

2,181,890

(79,815

)

2,102,075

The cost of inventories recognized as an expense for the year:


	Year ended December 31,
	2018			2019		2020
	NT$000			NT$000		NT$000
Cost of revenue		15,057,605			16,372,032		17,957,568
Loss on abandonment		5,497			12,369		5,323
Allowance for (reversal of ) inventory valuation and obsolescence loss		(13,070	)		27,341		16,317

		15,050,032			16,411,742		17,979,208

Reversal of allowance for inventory valuation and obsolescence loss was recognized due to the change in net realizable market value.

No inventories of the Group were pledged to others.

Non-current financial assets at fair value through other comprehensive income

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Non-current financial assets at fair value through other comprehensive income

11.	Non-current financial assets at fair value through other comprehensive income


	December 31, 2019		December 31, 2020
	NT$000		NT$000
Designation of equity instruments
Foreign unlisted stocks		38,534		38,534
Valuation adjustment		83,274		223,473

		121,808		262,007

Based on the Group’s business model, the foreign unlisted stocks held for strategic investments were elected to classify as “Financial assets at fair value through other comprehensive income”. As of December 31, 2019 and 2020, the fair value of aforementioned investments is the carrying amount at the end of each reporting period.

Amounts recognized in other comprehensive income in relation to the financial assets at fair value through other comprehensive income are listed below:


	Year ended December 31,
	2018		2019			2020
	NT$000		NT$000			NT$000
Financial assets at fair value through other comprehensive income
Foreign unlisted stocks		85,022		(52,549	)		140,199

No financial assets at fair value through other comprehensive income were pledged to others.

Information about fair value measurement is provided in Note 42 b).

Investments accounted for using equity method

12 Months Ended

Dec. 31, 2020

Investments accounted for using equity method [abstract]

Investments accounted for using equity method

12.	Investments accounted for using equity method


	December 31, 2019		December 31, 2020
	NT$000		NT$000
JMC ELECTRONICS CO., LTD. (“JMC”)		249,793		250,769
Unimos Microelectronics (Shanghai) Co., Ltd. (“Unimos Shanghai”)		3,143,117		3,020,908

		3,392,910		3,271,677

The basic information and summarized financial information of the associate that are material to the Group are as follows:

(a)

Basic information


		Shareholding ratio
Company name	Principal place of business	December 31, 2019	December 31, 2020	Nature of relationship	Method of measurement
Unimos Shanghai	Shanghai, PRC	45.02%	45.02%	Strategic Investee	Equity method

(b)

Summarized financial information

Statement of financial position


	Unimos Shanghai
	December 31, 2019			December 31, 2020
	NT$000			NT$000
Current assets		3,042,377			2,438,725
Non-current assets		3,499,819			3,905,089
Current liabilities		(459,502	)		(618,949	)
Non-current liabilities		(448,929	)		(248,583	)

Total net assets		5,633,765			5,476,282

Share in associate’s net assets		2,536,558			2,465,651
Depreciable assets		584,441			533,139
Goodwill		22,118			22,118

Carrying amount of the associate		3,143,117			3,020,908

Statement of comprehensive income


	Unimos Shanghai
	Year ended December 31,
	2018			2019			2020
	NT$000			NT$000			NT$000
Revenue		1,334,196			1,584,648			1,739,880

Loss for the year from continuing operations		(629,303	)		(352,008	)		(246,220	)
Other comprehensive income, net of income tax		—			—			—

Total comprehensive loss		(629,303	)		(352,008	)		(246,220	)

Dividends received from the associate		—			—			—

The carrying amount of the Group’s interests in all individually immaterial associates and the Group’s share of the operating results are summarized below:

As of December 31, 2019 and 2020, the carrying amount of the Group’s individually immaterial associates amounted to NT$

249,793

thousand and NT$250,769 thousand, respectively.


	Year ended December 31,
	2018			2019		2020
	NT$000			NT$000		NT$000
Profit for the year from continuing operations		41,933			63,838		14,833
Other comprehensive (loss) income, net of income tax		(2,687	)		5,732		23,143

Total comprehensive income		39,246			69,570		37,976

JMC has quoted market prices. As of December 31, 2019 and 2020, the fair value was NT$807,000 thousand and NT$454,010 thousand, respectively.

To further strengthen financial structure, increase balance of working capital and reduce debt ratio, the Company’s Board of Directors adopted a resolution on April 2, 2019 to dispose of 9,100,000 common shares of JMC, which reduced the shareholding of equity investment in JMC to 10%. The disposal of shares was completed on April 8, 2019 for cash consideration of NT$1,180,179 thousand, and the Company recognized gain on disposal of investment in associates amounted to NT$973,609 thousand. JMC is still recognized as investment in associates given that the Company retains significant influence by holding two seats in JMC’s Board of Directors.

Property, plant and equipment, net

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Property, plant and equipment, net

13.	Property, plant and equipment, net


	2018
	Land		Buildings			Machinery and equipment			Tools			Others			Construction in progress and equipment to be inspected			Total
	NT$000		NT$000			NT$000			NT$000			NT$000			NT$000			NT$000
January 1
Cost		452,738		9,809,970			45,778,207			4,004,703			2,624,083			968,719			63,638,420
Accumulated depreciation and impairment		—		(5,890,884	)		(36,964,480	)		(3,314,234	)		(2,203,511	)		—			(48,373,109	)

		452,738		3,919,086			8,813,727			690,469			420,572			968,719			15,265,311

January 1		452,738		3,919,086			8,813,727			690,469			420,572			968,719			15,265,311
Additions		—		247,186			2,445,313			591,229			172,652			1,489,190			4,945,570
Disposals		—		—			(904	)		(11,745	)		(2,067	)		—			(14,716	)
Reclassifications		—		199,724			1,154,663			7,604			26,026			(1,388,017	)		—
Depreciation expenses		—		(457,265	)		(2,180,718	)		(535,378	)		(203,218	)		—			(3,376,579	)
Exchange adjustment		—		—			12			—			23			—			35

December 31		452,738		3,908,731			10,232,093			742,179			413,988			1,069,892			16,819,621

December 31
Cost		452,738		10,254,531			48,274,171			4,402,711			2,610,893			1,069,892			67,064,936
Accumulated depreciation and impairment		—		(6,345,800	)		(38,042,078	)		(3,660,532	)		(2,196,905	)		—			(50,245,315	)

		452,738		3,908,731			10,232,093			742,179			413,988			1,069,892			16,819,621


	2019
	Land		Buildings			Machinery and equipment			Tools			Others			Construction in progress and equipment to be inspected			Total
	NT$000		NT$000			NT$000			NT$000			NT$000			NT$000			NT$000
January 1
Cost		452,738		10,254,531			48,274,171			4,402,711			2,610,893			1,069,892			67,064,936
Accumulated depreciation and impairment		—		(6,345,800	)		(38,042,078	)		(3,660,532	)		(2,196,905	)		—			(50,245,315	)

		452,738		3,908,731			10,232,093			742,179			413,988			1,069,892			16,819,621

January 1		452,738		3,908,731			10,232,093			742,179			413,988			1,069,892			16,819,621
Effects on initial application of IFRS 16		—		—			—			—			(31,904	)		—			(31,904	)

Adjusted balance at January 1		452,738		3,908,731			10,232,093			742,179			382,084			1,069,892			16,787,717
Additions		—		116,238			2,334,358			781,465			224,287			1,440,308			4,896,656
Disposals		—		—			(16,033	)		(9,336	)		(416	)		—			(25,785	)
Reclassifications		—		455,792			1,111,715			7,880			25,042			(1,573,811	)		26,618
Depreciation expenses		—		(384,832	)		(2,489,070	)		(625,712	)		(196,201	)		—			(3,695,815	)
Impairment losses		—		—			(9,938	)		—			—			—			(9,938	)
Exchange adjustment		—		—			(4	)		—			(5	)		—			(9	)

December 31		452,738		4,095,929			11,163,121			896,476			434,791			936,389			17,979,444

December 31
Cost		452,738		10,821,972			51,244,512			5,008,321			1,937,755			936,389			70,401,687
Accumulated depreciation and impairment		—		(6,726,043	)		(40,081,391	)		(4,111,845	)		(1,502,964	)		—			(52,422,243	)

		452,738		4,095,929			11,163,121			896,476			434,791			936,389			17,979,444


	2020
	Land		Buildings			Machinery and equipment			Tools			Others			Construction in progress and equipment to be inspected			Total
	NT$000		NT$000			NT$000			NT$000			NT$000			NT$000			NT$000
January 1
Cost		452,738		10,821,972			51,244,512			5,008,321			1,937,755			936,389			70,401,687
Accumulated depreciation and impairment		—		(6,726,043	)		(40,081,391	)		(4,111,845	)		(1,502,964	)		—			(52,422,243	)

		452,738		4,095,929			11,163,121			896,476			434,791			936,389			17,979,444

January 1		452,738		4,095,929			11,163,121			896,476			434,791			936,389			17,979,444
Additions		—		132,572			592,565			409,832			142,776			2,855,870			4,133,615
Disposals		—		—			(8,940	)		(3,121	)		(7,297	)		—			(19,358	)
Reclassifications		—		258,421			2,336,238			398,798			159,195			(3,152,652	)		—
Depreciation expenses		—		(394,636	)		(2,734,667	)		(749,624	)		(220,066	)		—			(4,098,993	)
Exchange adjustment		—		—			(20	)		—			(2	)		—			(22	)

December 31		452,738		4,092,286			11,348,297			952,361			509,397			639,607			17,994,686

December 31
Cost		452,738		11,212,129			53,246,474			5,451,547			2,185,299			639,607			73,187,794
Accumulated depreciation and impairment		—		(7,119,843	)		(41,898,177	)		(4,499,186	)		(1,675,902	)		—			(55,193,108	)

		452,738		4,092,286			11,348,297			952,361			509,397			639,607			17,994,686

Amount of borrowing costs capitalized as part of property, plant and equipment and the range of the interest rates for such capitalization are as follows:


	Year ended December 31,
	2018			2019			2020
	NT$000			NT$000			NT$000
Amount of interest capitalized		18,542			15,114			9,762
Range of the interest rates for capitalization		1.7582	%		1.7822	%		1.4909	%

Information about the property, plant and equipment that were pledged to others as collaterals is provided in Note 37.

Leasing arrangements - leasee

12 Months Ended

Dec. 31, 2020

Presentation of leases for lessee [abstract]

Leasing arrangements - leasee

14.	Leasing arrangements - lessee

The Group leases various assets, including land, buildings, machinery and equipment, and others. Lease agreements are typically made for periods of 2 to 30 years. Lease terms are negotiated on an individual basis and contain a wide range of different terms and conditions. The lease agreements do not impose covenants, but leased assets may not be used as security for borrowing purposes.

The carrying amount of

right-of-use

assets and the depreciation expenses are as follows:


	December 31, 2019		December 31, 2020
	Carrying amount		Carrying amount
	NT$000		NT$000
Land		669,967		636,261
Buildings		15,043		19,044
Machinery and equipment		—		203,249
Others		2,058		515

		687,068		859,069


	Year ended December 31,
	2019		2020
	Depreciation expenses		Depreciation expenses
	NT$000		NT$000
Land		22,657		20,938
Buildings		7,113		7,819
Machinery and equipment		4,520		46,225
Others		1,809		1,544

		36,099		76,526

For the years ended December 31, 2019 and 2020, additions to

right-of-use

assets were NT$11,183 thousand and NT$261,798 thousand, respectively.

The information on profit or loss accounts relating to lease contracts is as follows:


	Year ended December 31,
	2019		2020
	NT$000		NT$000
Items affecting profit or loss
Interest expense on lease liabilities		14,349		13,442
Expense on short-term lease contracts		230,589		202,782

For the years ended December 31, 2019 and 2020, the Group’s total cash outflow for leases were NT$273,709 thousand and NT$274,727 thousand, respectively.

Accounts payable

12 Months Ended

Dec. 31, 2020

Disclosure Of Detailed Information Of Trade And Other Payable Explanatory [Abstract]

Accounts payable

15.	Accounts payable


	December 31, 2019		December 31, 2020
	NT$000		NT$000
Accounts payable		419,520		766,805
Estimated accounts payable		400,028		200,016

		819,548		966,821

Other Payables

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Other Payables

16.	Other payables


	December 31, 2019		December 31, 2020
	NT$000		NT$000
Payables to contractors and equipment suppliers		972,770		1,145,359
Employees’ compensation payable		338,356		332,080
Salaries and bonuses payable		741,027		788,720
Pension payable		31,009		15,159
Directors’ remuneration payable		16,918		16,604
Interest payable		889		1,958
Other expense payable		876,067		949,523

		2,977,036		3,249,403

Long-term bank loans

12 Months Ended

Dec. 31, 2020

Statement [LineItems]

Long-term bank loans

17.	Long-term bank loans


Type of loans	Period and payment term	December 31, 2019			December 31, 2020
		NT$000			NT$000
Syndicated bank loan	Borrowing period is from May 30, 2018 to May 30, 2023; interest is repayable monthly; principal is repayable semi-annually from November 30, 2018		9,066,000			3,310,000
Government granted bank loans	Borrowing period is from March 11, 2020 to February 15, 2030; interest is repayable monthly; principal is repayable monthly from March 15, 2023		—			4,505,000
Less: Fee on syndicated bank loan			(24,355	)		(17,223	)
Less: Unamortized interest on government granted bank loans			—			(64,212	)
Less: Current portion (fee included)			(748,419	)		(748,353	)

			8,293,226			6,985,212

Interest rate range			1.7895	%		0.65%~1.7895	%

Unused credit lines of long-term NT$000			1,800,000			11,239,000

On January 1, 2019, Ministry of Economic Affairs, ROC (“MOEA”) implemented the “Action Plan for Welcoming Overseas Taiwanese Businesses to Return to Invest in Taiwan” and companies are subsidized with preferential interest loans for qualified investment projects. The Company has obtained the qualification from the MOEA, and signed loan agreements with financial institutions during January and March 2020 with the line of credit amounted to NT$12.144 billion and terms from seven to ten years. Funding from these loans was used to invest in machineries, equipment and plant expansions and broaden the Company’s working capital.

On May 15, 2018, the Company entered into a syndicated loan with eleven banks in Taiwan, including Taiwan Cooperative Bank, in the amount of NT$12 billion with a term of five years. Funding from this syndicated loan was used to repay the existing debt of financial institutions and broaden the Company’s working capital. Pursuant to the syndicated loan agreement, the Group is required to maintain certain financial ratios including current ratio, interest protection multiples and debt to equity ratio during the loan periods.

Information about the items related to the long-term bank loans that are pledged to others as collaterals is provided in Note 37.

Pensions

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Pensions

18.

Pensions

Defined Benefit Plans

The Company has a defined benefit pension plan in accordance with the Labor Standards Act, covering all regular employees’ service years prior to the enforcement of the Labor Pension Act on July 1, 2005 and service years thereafter of employees who chose to continue to be subject to the pension mechanism under the Labor Standards Act. Under the defined benefit pension plan, two units are accrued for each year of service for the first 15 years and one unit for each additional year thereafter, subject to a maximum of 45 units. Pension benefits are based on the number of units accrued and the average monthly salaries and wages of the last 6 months prior to retirement. The Company contributes monthly an amount equal to 2% of the employees’ monthly salaries and wages to the pension fund deposited with the Bank of Taiwan, the trustee, under the name of the independent pension fund committee. Also, the Company would assess the balance in the aforementioned labor pension reserve account by the end of every year. If the account balance is insufficient to pay the pension calculated by the aforementioned method, to the employees expected to be qualified for retirement next year, the Company will make contributions to cover the deficit by March of following year.

(a)

The amounts recognized in the statements of financial position are as follows:


	December 31, 2019			December 31, 2020
	NT$000			NT$000
Present value of defined benefit obligations		(901,159	)		(943,391	)
Fair value of plan assets		421,052			431,740

Net defined benefit liability		(480,107	)		(511,651	)

(b)

Movements in net defined benefit liability are as follows:


	2018
	Present value of defined benefit obligations			Fair value of plan assets			Net defined benefit liability
	NT$000			NT$000			NT$000
January 1		(838,543	)		360,017			(478,526	)
Current services cost		(382	)		—			(382	)
Interest (expense) income		(14,429	)		6,291			(8,138	)

		(853,354	)		366,308			(487,046	)

Remeasurements:
Return on plan assets (excluding amounts included in interest income or expense)		—			8,145			8,145
Financial assumption movement effect		(56,934	)		—			(56,934	)
Experience adjustments		(11,172	)		—			(11,172	)

		(68,106	)		8,145			(59,961	)

Pension fund contribution		—			26,242			26,242
Paid pension		11,379			(11,379	)		—

December 31		(910,081	)		389,316			(520,765	)


	2019
	Present value of defined benefit obligations			Fair value of plan assets			Net defined benefit liability
	NT$000			NT$000			NT$000
January 1		(910,081	)		389,316			(520,765	)
Current services cost		(332	)		—			(332	)
Interest (expense) income		(11,170	)		4,831			(6,339	)

		(921,583	)		394,147			(527,436	)

Remeasurements:
Return on plan assets (excluding amounts included in interest income or expense)		—			12,601			12,601
Financial assumption movement effect		(27,993	)		—			(27,993	)
Experience adjustments		36,308			—			36,308

		8,315			12,601			20,916

Pension fund contribution		—			26,413			26,413
Paid pension		12,109			(12,109	)		—

December 31		(901,159	)		421,052			(480,107	)


	2020
	Present value of defined benefit obligations			Fair value of plan assets			Net defined benefit liability
	NT$000			NT$000			NT$000
January 1		(901,159	)		421,052			(480,107	)
Current services cost		(263	)		—			(263	)
Interest (expense) income		(8,835	)		4,171			(4,664	)

		(910,257	)		425,223			(485,034	)

Remeasurements:
Return on plan assets (excluding amounts included in interest income or expense)		—			12,568			12,568
Financial assumption movement effect		(57,180	)		—			(57,180	)
Experience adjustments		(7,378	)		—			(7,378	)

		(64,558	)		12,568			(51,990	)

Pension fund contribution		—			25,373			25,373
Paid pension		31,424			(31,424	)		—

December 31		(943,391	)		431,740			(511,651	)

(c)

The Bank of Taiwan was commissioned to manage the fund of the Company’s defined benefit pension plan in accordance with the fund’s annual investment and utilization plan and the “Regulations for Revenues, Expenditures, Safeguard and Utilization of the Labor Retirement Fund” (Article 6: The scope of utilization for the fund includes deposit in domestic or foreign financial institutions, investment in domestic or foreign listed,

over-the-counter,

or private placement equity securities, investment in domestic or foreign real estate securitization products, etc.). With regard to the utilization of the fund, its minimum earnings in the annual distributions on the final financial statements shall be no less than the earnings attainable from the amounts accrued from

two-year

time deposits with the interest rates offered by local banks. If the earnings are less than aforementioned rates, government shall make payment for the deficit after being authorized by the authority. The Company has no right to participate in managing and operating that fund and hence the Company is unable to disclose the classification of the fair value of plan asset in accordance with IAS 19 “Employee Benefits” paragraph 142. The composition of fair value of plan assets as of December 31, 2019 and 2020 is given in the Annual Labor Retirement Fund Utilization Report announced by the government.

(d)

The principal actuarial assumptions used were as follows:


	Year ended December 31,
	2019			2020
Discount rate		1.00	%		0.50	%

Future salary increase		3.50	%		3.50	%

Assumptions regarding future mortality are set based on actuarial advice in accordance with published statistics and experience in each territory.

Because the main actuarial assumption changed, the present value of defined benefit obligations is affected. The analysis was as follows:


	Discount rate					Future salary increase
	Increase 0.25%			Decrease 0.25%		Increase 0.25%		Decrease 0.25%
	NT$000			NT$000		NT$000		NT$000
December 31, 2019
Effect on present value of defined benefit obligations		(27,993	)		29,284		28,501		(27,407	)

December 31, 2020
Effect on present value of defined benefit obligations		(29,114	)		30,434		29,471		(28,365	)

The sensitivity analysis above is based on a change in an assumption while holding all other assumptions constant. In practice, changes in some of the assumptions may be correlated. The method of sensitivity analysis and the method of calculating net defined benefit liability in the statements of financial position are the same.

The methods and types of assumptions used in preparing the sensitivity analysis remain unchanged from previous period.

(e)

Expected contributions to the defined benefit pension plans of the Company for the year ending December 31, 2021 amounts to NT$26,261 thousand.

(f)

As of December 31, 2020, the weighted average duration of that retirement plan is 12.6 years. The analysis of timing of the future pension payment was as follows:


	December 31, 2020
	NT$000
Within 1 year		35,066
1-2 years		35,198
2-5 years		122,969
5-10 years		165,979

		359,212

Defined Contribution Plans

Effective from July 1, 2005, the Company established a defined contribution pension plan (“New Plan”) under the Labor Pension Act, covering all regular employees with ROC nationality. Under the New Plan, the Company contributes monthly an amount based on 6% of the employees’ monthly salaries and wages to the employees’ individual pension accounts at the Bureau of Labor Insurance. The benefits accrued are paid monthly or in lump sum upon termination of employment. The pension costs under defined contribution pension plans of the Company for the years ended December 31, 2018, 2019 and 2020 were NT$193,047 thousand, NT$187,502 thousand and NT$184,562 thousand, respectively.

Share-based payments

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Share-based payments

19.	Share-based payments

Restricted shares

On July 14, 2015, the Company’s Board of Directors approved the issuance of restricted shares. The record dates for the shares issuance were July 21, 2015 and May 10, 2016. The relevant information is as follows:

Type of

arrangement

Grant
date

Share price
on grant date
(in NT$)

Number of
shares
(in thousands)

Contract
period

Vesting condition

Restricted shares award agreement

July 21,
2015

36.1

15,752

3 years

Meet service and performance conditions

Restricted shares award agreement

May 10,
2016

30.6

1,548

3 years

Meet service and performance conditions

The restricted shares issued by the Company cannot be transferred during the vesting period, but voting right and dividend right are not restricted. Employees are required to return the shares but not required to return the dividends received if they resign during the vesting period. When the employees accomplish the years of service and performance conditions, the received restricted shares will be vested based on the vesting ratio.

As of December 31, 2019, there were no outstanding restricted shares.

The expenses incurred on share-based payment transactions for the years ended December 31,

2018 and 2019 were NT$41,043 thousand and NT$822 thousand, respectively.

Capital stock

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Capital stock

20.	Capital stock

As of December 31, 2020, the Company’s authorized capital was NT$9,700,000 thousand, consisting of 970,000 thousand ordinary shares, and the

paid-in

capital was NT$7,272,401 thousand with a par value of NT$10 per share, consisting of 727,240 thousand ordinary shares. All proceeds from shares issued have been collected.

As of December 31, 2020, the outstanding ADSs were approximately 4,270,600 units representing 85,412 thousand ordinary shares and each ADS represents 20 ordinary shares of the Company. The major terms and conditions of the ADSs are summarized as follows:

(a)

Voting rights:

ADS holders have no right to directly vote in shareholders’ meetings with respect to the deposited shares. The depository bank shall vote on behalf of ADS holders or provide voting instruction to the designated person of the Company. The depository bank shall vote in the manner as instructed by ADS holders.

(b)

Distribution of dividends:

ADS holders are deemed to have the same rights as holders of ordinary shares with respect to the distribution of dividends.

Movements in the number of the Company’s ordinary shares outstanding are as follows:


	2018			2019			2020
	in thousands			in thousands			in thousands
January 1		856,059			727,265			727,240
Restricted shares – cancelled		(349	)		(25	)		—
Restricted shares – uncancelled		(23	)		—			—
Capital reduction		(128,422	)		—			—

December 31		727,265			727,240			727,240

Treasury stock

(a)

On March 7, 2019 and August 6, 2019, the Company’s Board of Directors approved the cancellation of treasury stock 25,570 thousand shares amounted to NT$962,503 thousand. As of December 31, 2019, all of the Company’s treasury stocks were cancelled. As of December 31, 2018, the reasons for share repurchases and movements in the number of the Company’s treasury stock is as follows:


	2018
	Shares			Amount
	in thousands			NT$000
January 1		30,085			1,007,654
Capital reduction		(4,515	)		(45,151	)

December 31		25,570			962,503

(b)

Pursuant to the ROC Securities and Exchange Act, the number of shares repurchased as treasury stock may not exceed 10% of the number of the Company’s issued shares and the amount bought back may not exceed the sum of retained earnings,

paid-in

capital in excess of par value and realized capital surplus.

(c)

Pursuant to the ROC Securities and Exchange Act, treasury stock may not be pledged as collateral and is not entitled to dividends before it is reissued.

(d)

Pursuant to the ROC Securities and Exchange Act, treasury stock should be reissued to the employees within five years from the reacquisition date and shares not reissued within the five-year period are to be retired. Treasury stock to enhance the Company’s credit rating and the stockholders’ equity should be retired within six months from acquisition.

In order to adjust capital structure and increase return of equity, the Company’s shareholders adopted a resolution on June 26, 2018 to reduce capital stock and return cash to shareholders. Subsequently, the record date of the capital reduction was fixed on August 15, 2018, and capital was reduced approximately 15% amounted to NT$1,329,446 thousand consisting of 132,945 thousand ordinary shares.

Capital surplus

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Capital surplus

21.	Capital surplus

Pursuant to the ROC Company Act, any capital surplus arising from

paid-in

capital in excess of par value on issuance of ordinary shares and donations can be used to cover accumulated deficits or to issue new shares or cash to shareholders in proportion to their share ownership, provided that the Company has no accumulated deficits. Furthermore, the ROC Securities and Exchange Act requires that the amount of capital surplus to be capitalized mentioned above may not exceed 10% of the

paid-in

capital each year. The capital surplus may not be used to cover accumulated deficits unless the legal reserve is insufficient.


	2018
	Share premium		Employee restricted shares			Others		Total
	NT$000		NT$000			NT$000		NT$000
January 1		5,873,743		390,401			7,304		6,271,448
Share-based payments		—		(7,967	)		—		(7,967	)
Capital reduction		—		72			—		72

December 31		5,873,743		382,506			7,304		6,263,553


	2019
	Share premium			Employee restricted shares			Others		Total
	NT$000			NT$000			NT$000		NT$000
January 1		5,873,743			382,506			7,304		6,263,553
Share-based payments		—			(412	)		—		(412	)
Cancellation of treasury stock		(199,501	)		(12,853	)		—		(212,354	)

December 31		5,674,242			369,241			7,304		6,050,787


	2020
	Share premium		Employee restricted shares			Others		Total
	NT$000		NT$000			NT$000		NT$000
January 1		5,674,242		369,241			7,304		6,050,787
Reclassifications		369,241		(369,241	)		—		—

December 31		6,043,483		—			7,304		6,050,787

Retained earnings

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Retained earnings

22.	Retained earnings

Under the Company’s Articles of Incorporation, the current year’s earnings, if any, shall first be used to pay all taxes and offset prior years’ operating losses and then 10% of the remaining amount shall be set aside as a legal reserve. The Company may then appropriate or reverse a certain amount as special reserve according to the relevant regulations. After the distribution of earnings, the remaining earnings and prior years’ unappropriated retained earnings may be appropriated according to a proposal by the Board of Directors and approved in the shareholders’ meeting.

The Company’s dividend policy is summarized here. As the Company operates in a volatile business environment, the issuance of dividends to be distributed takes into consideration the Company’s financial structure, operating results and future expansion plans. The earnings distribution of the Company may be made by way of cash dividends or stock dividends, provided that cash dividends account for at least 10% of the total dividends distributed. The earnings distribution will be proposed by the Board of Directors and approved at the shareholders’ meeting.

Except for covering accumulated deficits or issuing new shares or cash to shareholders in proportion to their share ownership, the legal reserve may not be used for any other purpose. The use of the legal reserve for the issuance of shares or cash to shareholders in proportion to their share ownership is permitted, provided that the distribution of the reserve is limited to the portion in excess of 25% of the Company’s

paid-in

capital.

In accordance with the regulations, the Company must set aside a special reserve from the debit balance on other equity items at the statements of financial position date before distributing earnings. When the debit balance on other equity items is reversed subsequently, the reversed amount may be included in the distributable earnings.

The appropriations of 2017, 2018 and 2019 earnings were resolved in the shareholders’ meetings held on June 26, 2018, June 10, 2019 and June 9, 2020, respectively. The appropriations and dividends per share are as follows:


	2017				2018				2019
	Amount		Cash Distribution per share		Amount		Cash Distribution per share		Amount		Cash Distribution per share
	Amount		Cash Distribution per share		Amount		Cash Distribution per share		Amount		Cash Distribution per share
	NT$000		NT$		NT$000		NT$		NT$000		NT$
Legal reserve		302,653				110,308				258,416
Special reserve		—				—				19,802
Cash dividend		256,806		0.30		872,718		1.20		1,309,032		1.80

The information relating to employees’ compensation and directors’ remuneration is provided in Note 31.

Other equity interest

12 Months Ended

Dec. 31, 2020

Other reserves [abstract]

Other equity interest

23.	Other equity interest


	2018
	Financial statements translation differences of foreign operations			Unrealized gain (loss) on valuation of financial assets at fair value through other comprehensive income			Unrealized gain on valuation of available-for-sale financial assets			Unearned employee awards			Total
	NT$000			NT$000			NT$000			NT$000			NT$000
January 1		65,593			—			678			(54,570	)		11,701
Effects on initial application of IFRS 9		—			42,843			(678	)		—			42,165

Adjusted beginning balance		65,593			42,843			—			(54,570	)		53,866
Currency translation differences
- The Company		(51,077	)		—			—			—			(51,077	)
Employee restricted shares
- The Company		—			—			—			52,869			52,869
Evaluation adjustment
- The Company		—			85,022			—			—			85,022
- Associates		—			(2,438	)		—			—			(2,438	)
Evaluation adjustment related tax
- The Company		—			(18,529	)		—			—			(18,529	)

December 31		14,516			106,898			—			(1,701	)		119,713


	2019
	Financial statements translation differences of foreign operations			Unrealized gain (loss) on valuation of financial assets at fair value through other comprehensive income			Unearned employee awards			Total
	NT$000			NT$000			NT$000			NT$000
January 1		14,516			106,898			(1,701	)		119,713
Currency translation differences
- The Company		(104,198	)		—			—			(104,198	)
Employee restricted shares
- The Company		—			—			1,701			1,701
Evaluation adjustment
- The Company		—			(52,549	)		—			(52,549	)
- Associates		—			5,093			—			5,093
Evaluation adjustment related tax
- The Company		—			7,016			—			7,016
Disposal of investment accounted for using equity method		—			(72	)		—			(72	)

December 31		(89,682	)		66,386			—			(23,296	)


	2020
	Financial statements translation differences of foreign operations			Unrealized gain (loss) on valuation of financial assets at fair value through other comprehensive income			Total
	NT$000			NT$000			NT$000
January 1		(89,682	)		66,386			(23,296	)
Currency translation differences
- The Company		28,352			—			28,352
Evaluation adjustment
- The Company		—			140,199			140,199
- Associates		—			22,925			22,925
Evaluation adjustment related tax
- The Company		—			(34,794	)		(34,794	)

December 31		(61,330	)		194,716			133,386

Revenue

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Revenue

24.

Revenue


	Year ended December 31,
	2018		2019		2020
	NT$000		NT$000		NT$000
Revenue from contracts with customers		18,480,027		20,337,881		23,011,381

The Group is primarily engaged in the assembly and testing services on high-integration and high-precision integrated circuits, and recognized revenue based on the progress towards completion of performance obligation during the service period. Information on revenue disaggregation is provided in Note 43.

Contract assets and liabilities

The Group has recognized the following contract assets and liabilities in relation to revenue from contracts with customers:


	January 1, 2019		December 31, 2019		December 31, 2020
	NT$000		NT$000		NT$000
Contract assets		299,835		377,869		389,016

Contract liabilities (Advance payments)		1,432		1,231		—

The information relating to loss allowance for contract assets is provided in Note 42 a).

Revenue recognized for the years ended as of December 31, 2019 and 2020, amounted to NT$766 thousand and NT$565 thousand, respectively, was related to carried forward contract liabilities for performance obligations not satisfied in prior year.

All of the service contracts are for periods of one year or less. As permitted under IFRS 15, “Revenue from Contracts with Customers”, the transaction price allocated to these unsatisfied contracts is not disclosed.

Other income (expenses), net

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Other income (expenses), net

25.	Other income (expenses), net


	Year ended December 31,
	2018			2019			2020
	NT$000			NT$000			NT$000
Gain on disposal of scrapped materials		59,380			43,652			51,077
Royalty income		43,224			12,336			2,962
Gain on disposal of items purchased on behalf of others		31,268			15,080			30,140
Gain on disposal of property, plant and equipment, net		14,274			20,271			48,070
Insurance compensation income		147			10,435			—
Impairment loss on property, plant and equipment		—			(9,938	)		—
Others		(779	)		1,092			3,329

		147,514			92,928			135,578

Interest income

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Interest income

26.	Interest income


	Year ended December 31,
	2018		2019		2020
	NT$000		NT$000		NT$000
Bank deposits		49,051		59,901		25,547
Imputed interest from deposits		—		—		25
Financial assets at amortized cost		920		4,467		2,206

		49,971		64,368		27,778

Other income

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Other income

27.	Other income


	Year ended December 31,
	2018		2019		2020
	NT$000		NT$000		NT$000
Rental income		7,819		9,249		10,260
Dividend income		571		585		3,229
Grant income		—		925		7,668

		8,390		10,759		21,157

Other gains and losses

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Other gains and losses

28.	Other gains and losses


	Year ended December 31,
	2018		2019			2020
	NT$000		NT$000			NT$000
Foreign exchange gains (losses), net		93,104		(154,993	)		(355,255	)
Reimbursement of ADSs service charge		13,269		4,292			2,101
Gain on valuation of financial assets at fair value through profit or loss		1,485		1,317			24,015
Others		6,851		970			5,872

		114,709		(148,414	)		(323,267	)

Finance costs

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Finance costs

29.	Finance costs


	Year ended December 31,
	2018			2019			2020
	NT$000			NT$000			NT$000
Interest expense
Bank loans		170,476			171,840			158,720
Lease liabilities		—			14,349			13,442
Lease obligations payable		482			—			—
Less: Amounts capitalized in qualifying assets		(18,542	)		(15,114	)		(9,762	)

		152,416			171,075			162,400
Finance expense		37,832			9,187			9,082

		190,248			180,262			171,482

Expenses by nature

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Expenses by nature

30.	Expenses by nature


	Year ended December 31,
	2018		2019		2020
	NT$000		NT$000		NT$000
Raw materials and supplies used		3,079,909		3,575,283		4,708,493
Employee benefit expenses		5,606,833		6,075,773		6,010,227
Depreciation expenses		3,376,579		3,731,914		4,175,519
Others		4,464,499		4,590,720		4,686,218

		16,527,820		17,973,690		19,580,457

Employee benefit expenses

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Employee benefit expenses

31.	Employee benefit expenses


	Year ended December 31,
	2018		2019		2020
	NT$000		NT$000		NT$000
Salaries		4,628,039		5,114,790		4,937,591
Directors’ remuneration		18,456		26,266		28,229
Labor and health insurance		406,111		422,106		396,796
Pension		201,567		194,173		189,489
Share-based payments		41,043		822		—
Other personnel expenses		311,617		317,616		458,122

		5,606,833		6,075,773		6,010,227

In accordance with the Company’s Articles of Incorporation, employees’ compensation is based on the current year’s earnings, which should first be used to cover accumulated deficits, if any, and then 10% of the remaining balance distributed as employees’ compensation, including distributions to certain qualifying employees in affiliate companies, and no more than 0.5% as directors’ remuneration. Subject to the Board of Directors’ approval, employees’ compensation may be made by way of cash or share issuance. Distribution of employees’ compensation and directors’ remuneration shall be presented and reported in the subsequent shareholders’ meeting.

Based on profit distributable as of the end of reporting period, for the years ended December 31, 2018, 2019 and 2020, the employees’ compensation were accrued at NT$199,027 thousand, NT$338,356 thousand and NT$332,080 thousand, respectively; the directors’ remuneration were accrued at NT$9,951 thousand, NT$16,918 thousand and NT$16,604 thousand, respectively.

For the year of 2019, employees’ compensation and directors’ remuneration recognized were consistent with the amounts resolved in the Board of Directors’ meetings.

Income tax expense

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Income tax expense

32.	Income tax expense

Income tax expense

(a)

Components of income tax expense:


	Year ended December 31,
	2018			2019			2020
	NT$000			NT$000			NT$000
Current income tax:
Current income tax on profits for the period		326,057			408,788			636,876
Income tax on unappropriated retained earnings		28,165			74,540			105,665
Prior year income tax under (over) estimation		3,729			(5,016	)		(133,923	)

Total current income tax		357,951			478,312			608,618

Deferred income tax:
Relating to origination and reversal of temporary differences		101,441			35,367			(14,237	)
Impact of change in tax rate		(2,774	)		—			—

Total deferred income tax		98,667			35,367			(14,237	)

Income tax expense		456,618			513,679			594,381

(b)

The income tax (charge)/credit relating to components of other comprehensive income are as follows:


	Year ended December 31,
	2018			2019			2020
	NT$000			NT$000			NT$000
Unrealized gain (loss) on valuation of financial assets at fair value through other comprehensive income		17,005			(7,016	)		34,794
Remeasurement of defined benefit obligations		(11,992	)		4,183			(10,398	)
Impact of change in tax rate		(887	)		—			—

		4,126			(2,833	)		24,396

Reconciliation of income tax expense and the accounting profit:


	Year ended December 31,
	2018			2019			2020
	NT$000			NT$000			NT$000
Tax calculated based on profit before tax and statutory tax rate		356,488			606,917			595,258
Effects from adjustments based on regulation		81,042			(162,924	)		26,974
Temporary difference not recognized as deferred tax assets		(10,951	)		(608	)		(4	)
Prior year income tax under (over) estimation		3,729			(5,016	)		(133,923	)
Income tax on unappropriated retained earnings		28,165			74,540			105,665
Impact of change in tax rate		(2,774	)		—			—
Effect of different tax rates in countries in which the Group operates		919			770			411

Income tax expense		456,618			513,679			594,381

The amounts of deferred tax assets or liabilities resulting from temporary differences and investment tax credits are as follows:


	2018
	January 1			Effects on initial application of IFRS 9 and IFRS 15			Recognized in profit or loss			Recognized in other comprehensive income			December 31
	NT$000			NT$000			NT$000			NT$000			NT$000
Deferred tax assets
Loss on inventories		9,132			(770	)		(1,130	)		—			7,232
Property, plant and equipment		55,494			—			8,689			—			64,183
Provisions		21,643			—			(9,247	)		—			12,396
Deferred revenue		39,485			—			(5,329	)		—			34,156
Net defined benefit liability		78,451			—			7,889			14,403			100,743
Unrealized exchange losses		8,167			144			(4,736	)		—			3,575
Investment tax credit		—			—			4,420			—			4,420
Others		—			—			11			—			11

Total		212,372			(626	)		567			14,403			226,716

Deferred tax liabilities
Property, plant and equipment		(174,293	)		—			(107,301	)		—			(281,594	)
Contract assets		—			(8,067	)		8,067			—			—
Financial assets at fair value through other comprehensive income		—			(8,636	)		—			(18,529	)		(27,165	)

Total		(174,293	)		(16,703	)		(99,234	)		(18,529	)		(308,759	)

Information presented on statements of financial position:
Deferred tax assets		212,372												226,716

Deferred tax liabilities		(174,293	)											(308,759	)


	2019
	January 1			Recognized in profit or loss			Recognized in other comprehensive income			December 31
	NT$000			NT$000			NT$000			NT$000
Deferred tax assets
Loss on inventories		7,232			5,468			—			12,700
Property, plant and equipment		64,183			(25,515	)		—			38,668
Provisions		12,396			(6,796	)		—			5,600
Deferred revenue		34,156			(6,506	)		—			27,650
Net defined benefit liability		100,743			(3,948	)		(4,183	)		92,612
Unrealized exchange losses		3,575			13,721			—			17,296
Investment tax credit		4,420			(4,420	)		—			—
Others		11			15			—			26

Total		226,716			(27,981	)		(4,183	)		194,552

Deferred tax liabilities
Property, plant and equipment		(281,594	)		(7,386	)		—			(288,980	)
Financial assets at fair value through other comprehensive income		(27,165	)		—			7,016			(20,149	)

Total		(308,759	)		(7,386	)		7,016			(309,129	)

Information presented on statements of financial position
Deferred tax assets		226,716									194,552

Deferred tax liabilities		(308,759	)								(309,129	)


	2020
	January 1			Recognized in profit or loss			Recognized in other comprehensive income			December 31
	NT$000			NT$000			NT$000			NT$000
Deferred tax assets
Loss on inventories		12,700			3,263			—			15,963
Property, plant and equipment		38,668			(2,267	)		—			36,401
Provisions		5,600			(2,922	)		—			2,678
Deferred revenue		27,650			(6,506	)		—			21,144
Net defined benefit liability		92,612			(4,089	)		10,398			98,921
Unrealized exchange losses		17,296			(7,381	)		—			9,915
Others		26			643			—			669

Total		194,552			(19,259	)		10,398			185,691

Deferred tax liabilities
Property, plant and equipment		(288,980	)		33,496			—			(255,484	)
Financial assets at fair value through other comprehensive income		(20,149	)		—			(34,794	)		(54,943	)

Total		(309,129	)		33,496			(34,794	)		(310,427	)

Information presented on statements of financial position
Deferred tax assets		194,552									185,691

Deferred tax liabilities		(309,129	)								(310,427	)

The Company has not recognized taxable temporary differences associated with investments as deferred tax liabilities. As of December 31, 2019 and 2020, the amounts of temporary differences not recognized as deferred tax liability were NT$180,395 thousand and NT$45,005 thousand, respectively.

The Company’s income tax returns through 2018 have been assessed and approved by the Tax Authority.

On October 31, 2016, the Company merged with its former parent company, ChipMOS TECHNOLOGIES (Bermuda) LTD. And as a result, the Company recognized its own shares originally held by former parent company as treasury stock. Subsequently, the Company deducted unappropriated retained earnings by NT$5,052,343 thousand to reflect the loss due from the cancellation of treasury stock. In January 2017, the Company has filed an application to the National Taxation Bureau of the Northern Area, Ministry of Finance to apply the accumulated deficit amount, as a deduction in the calculation of years 2015 and 2016 additional 10% tax on unappropriated retained earnings. In April and June 2020, the Company received the Notice for Assessment of Tax for the years 2015 and 2016 from the National Taxation Bureau of the Northern Area, Ministry of Finance, and is entitled to tax refund amounted to NT$138,941 thousand.

Earnings per share

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Earnings per share

33.	Earnings per share

Year ended December 31, 2018

Amount

after income
tax

Weighted average
number of ordinary
shares outstanding

Earnings

per share

Basic earnings per share

NT$000

In thousands

NT$

Profit attributable to equity holders of the Company

1,325,824

802,725

1.65

Diluted earnings per share

Assumed conversion of all dilutive potential ordinary shares:

Employees’ compensation

7,626

Restricted shares

3,356

Profit attributable to equity holders of the Company

1,325,824

813,707

1.63

Year ended December 31, 2019

Amount

after income
tax

Weighted average

number of ordinary
shares outstanding

Earnings

per share

Basic earnings per share

NT$000

In thousands

NT$

Profit attributable to equity holders of the Company

2,508,574

727,111

3.45

Diluted earnings per share

Assumed conversion of all dilutive potential ordinary shares:

Employees’ compensation

9,879

Restricted shares

126

Profit attributable to equity holders of the Company

2,508,574

737,116

3.40

Year ended December 31, 2020

Amount

after income
tax

Weighted average
number of ordinary
shares outstanding

Earnings

per share

Basic earnings per share

NT$000

In thousands

NT$

Profit attributable to equity holders of the Company

2,378,978

727,240

3.27

Diluted earnings per share

Assumed conversion of all dilutive potential ordinary shares:

Employees’ compensation

9,668

Profit attributable to equity holders of the Company

2,378,978

736,908

3.23

Supplementary cash flow information

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Supplementary cash flow information

34.	Supplementary cash flow information

Partial cash paid for investing activities

Property, plant and equipment


	Year ended December 31,
	2018			2019			2020
	NT$000			NT$000			NT$000
Purchase of property, plant and equipment		4,945,570			4,896,656			4,133,615
Add: Beginning balance of payable to contractors and equipment suppliers		713,313			1,516,735			972,770
Add: Beginning balance of payable on lease		29,842			—			—
Less: Ending balance of payable to contractors and equipment suppliers		(1,516,735	)		(972,770	)		(1,145,359	)
Less: Ending balance of payable on lease		(17,792	)		—			—

Cash paid during the year		4,154,198			5,440,621			3,961,026

Changes in liabilities from financing activities

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Changes in liabilities from financing activities

35.	Changes in liabilities from financing activities


	2018
	Short-term bank loans			Long-term bank loans (including current portion)		Guarantee deposits			Total liabilities from financing activities
	NT$000			NT$000		NT$000			NT$000
January 1		969,353			9,642,021		1,371			10,612,745
Changes in cash flow from financing activities		(969,353	)		110,250		(279	)		(859,382	)
Amortization of loan fees		—			37,247		—			37,247

December 31		—			9,789,518		1,092			9,790,610


	2019
	Long-term bank loans (including current portion)			Guarantee deposits		Lease liabilities			Total liabilities from financing activities
	NT$000			NT$000		NT$000			NT$000
January 1		9,789,518			1,092		—			9,790,610
Effects on initial application of IFRS 16		—			—		884,275			884,275

Adjusted balance at January 1		9,789,518			1,092		884,275			10,674,885
Changes in cash flow from financing activities		(756,450	)		3		(48,161	)		(804,608	)
Adjustment to right-of-use assets		—			—		(148,512	)		(148,512	)
Reclassification to payable on equipment from lease liabilities		—			—		(9,000	)		(9,000	)
Amortization of loan fees		8,577			—		—			8,577
Amortization of interest expense		—			—		14,349			14,349

December 31		9,041,645			1,095		692,951			9,735,691


	2020
	Long-term bank loans (including current portion)			Guarantee deposits		Lease liabilities			Total liabilities from financing activities
	NT$000			NT$000		NT$000			NT$000
January 1		9,041,645			1,095		692,951			9,735,691
Changes in cash flow from financing activities		(1,326,857	)		575		(84,928	)		(1,411,210	)
Adjustment to right-of-use assets		—			—		249,030			249,030
Reclassification		—			20,000		—			20,000
Amortization of loan fees		7,581			—		—			7,581
Amortization of interest expense		11,196			—		13,442			24,638

December 31		7,733,565			21,670		870,495			8,625,730

Related party transactions

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Related party transactions

36.	Related party transactions

Parent and ultimate controlling party

The Company has neither a parent company nor an ultimate controlling party. The transactions between the Company and its subsidiaries were eliminated in the accompanying consolidated financial statements and were not disclosed herein. The transactions between the Group and other related parties are as follows.


	b)	Names of related parties and relationship


Name	Relationship
Unimos Shanghai		Associate
JMC		Associate

Significant related party transactions

(a)

Purchases of materials


	Year ended December 31,
	2018		2019		2020
	NT$000		NT$000		NT$000
JMC		132,494		9		—

Purchases of materials from associate is based on normal commercial terms and conditions. The payment terms of the purchases from associate have no significant differences with third party suppliers.

(b)

Acquisition of financial assets

In January 2018, ChipMOS BVI participated in Unimos Shanghai’s increase of

paid-in

capital based on its shareholding amounted to NT$794,694 thousand.


	d)	Key management personnel compensation


	Year ended December 31,
	2018		2019		2020
	NT$000		NT$000		NT$000
Salaries and other short-term employee benefits		151,095		178,713		186,854
Post-employment compensation		2,067		2,049		4,258
Share-based payments		6,763		—		—

		159,925		180,762		191,112

Pledged assets

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Pledged assets

37.	Pledged assets

Assets

Purpose

December 31,
2019

December 31,
2020

Carry
amount

NT$000

Non-current

financial assets at amortized cost

Lease and
bank loan

68,450

48,319

Property, plant and equipment, net

- Land

Bank loan

452,738

- Buildings

Bank loan

4,095,929

4,092,287

- Machinery and equipment

Bank loan

4,105,912

6,912,544

8,723,029

11,505,888

Significant contingent liabilities and unrecognized contract commitments

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Significant contingent liabilities and unrecognized contract commitments

38.	Significant contingent liabilities and unrecognized contract commitments

A letter of guarantee was issued by the Bank of Taiwan to the Customs Administration of the Ministry of Finance for making payment of customs-duty deposits when importing. As of December 31, 2019 and 2020, the amounts guaranteed by the Bank of Taiwan were NT$100,800 thousand and NT$99,000 thousand, respectively.

Capital expenditures that are contracted for, but not provided for are as follows:


	December 31, 2019		December 31, 2020
	NT$000		NT$000
Property, plant and equipment, net		1,640,712		2,331,041

Significant disaster loss

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Significant disaster loss

39.	Significant disaster loss

None.

Significant events after the reporting periods

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Significant events after the reporting periods

40.	Significant events after the reporting period

None.

Capital management

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Capital management

41.	Capital management

The Group’s objectives when managing capital are to safeguard the Group’s ability to continue as a going concern in order to provide returns for shareholders and to maintain an optimal capital structure to reduce the cost of capital. In order to maintain or adjust the capital structure, the Group may adjust the amount of dividends paid to shareholders, return capital to shareholders, issue new shares or sell assets to reduce debt. The Group monitors capital on the basis of the liabilities to assets ratio. Total capital is shown as “Equity” in the consolidated statements of financial position, which is also equal to total assets minus total liabilities.

The liabilities to assets ratio at December 31, 2019 and 2020 were as follows:


	December 31, 2019			December 31, 2020
	NT$000			NT$000
Total liabilities		14,775,302			14,364,975
Total assets		34,305,887			35,080,814

Liabilities to assets ratio		43.07	%		40.95	%

Financial risk management and fair values of financial instruments

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Financial risk management and fair values of financial instruments

42.	Financial risk management and fair values of financial instruments


	a)	Financial instruments

(a)

Financial instruments by category


	December 31, 2019		December 31, 2020
	NT$000		NT$000
Financial assets
Financial assets at fair value through profit or loss
Financial assets mandatorily measured at fair value through profit or loss		11,038		63,488
Financial assets at fair value through other comprehensive income
Designation of equity instruments		121,808		262,007
Financial assets at amortized cost
Cash and cash equivalents		4,704,084		4,113,651
Financial assets at amortized cost		237,420		254,801
Notes receivable		765		599
Accounts receivable		4,452,904		5,364,156
Accounts receivable – related parties		1,045		—
Other receivables		89,676		51,436
Other receivables – related parties		2,948		—
Refundable deposits		21,145		21,186

		9,642,833		10,131,324

Financial liabilities
Financial liabilities at amortized cost
Notes payable		—		2,899
Accounts payable		819,548		966,821
Other payables		2,977,036		3,249,403
Long-term bank loans (including current portion)		9,041,645		7,733,565
Guarantee deposits		1,095		21,670

		12,839,324		11,974,358

Lease liabilities (including current portion)		692,951		870,495

(b)

Risk management policies

The Group’s risk management objective is to manage the market risk, credit risk and liquidity risk related to its operating activities. The Group identifies, measures, and manages such risks by its policies and preferences.

ii)

The Group has established appropriate policies, procedures and internal controls for financial risk management. Before entering into significant financial transactions, a due approval process must be carried out by the Board of Directors based on related protocols and internal control procedures. The Group complies with its financial risk management policies at all times.

iii)

In order to minimize and manage financial risks, the Group’s overall risk management program focuses on analyzing, identifying, and evaluating financial risk factors that may potentially have adverse effects on the Group’s financial position, and provide feasible solutions to avoid those factors.

(c)

Significant financial risks and degrees of financial risks

Market risk

The Group’s market risk is the risk that the fair value or future cash flows of a financial instrument will fluctuate because of changes in market prices. Market risks comprise foreign currency risk, interest rate risk, and other price risks.

In practice, the risk variable rarely changes individually, and the change of each risk variable is usually correlative. The following sensitivity analysis did not consider the interaction of each risk variable.

Foreign exchange risk

The Group’s exposure to the risk of changes in foreign exchange rates relates primarily to the Group’s operating activities (when revenue or expense is denominated in a different currency from the Company’s and its subsidiaries’ functional currency) and the Group’s net investments in foreign operations.

The Group applies natural hedges by using accounts receivable and accounts payable denominated in the same currency. However, this natural hedge does not concur with the requirement for hedge accounting. Furthermore, as net investments in foreign operations are for strategic purposes, they are not hedged by the Group.

The Group’s foreign currency exposure gives rise to market risks associated with exchange rate movements against the NT dollar for cash and cash equivalents, accounts receivable, other receivables, bank loans, accounts payable and other payables.

The Group’s businesses involve some

non-functional

currency operations. The information on assets and liabilities denominated in foreign currencies whose values would be materially affected by the exchange rate fluctuations is as follows:


	December 31, 2019
	Foreign currency		Exchange rate		Carrying amount (NT$000)
(Foreign currency: functional currency)
Financial assets
Monetary items
US$000		188,369		29.9800		5,647,303
JPY000		266,819		0.2760		73,642
RMB000		6,197		4.3050		26,678
Non-monetary items
JPY000		441,334		0.2760		121,808
RMB000		730,108		4.3050		3,143,117
Financial liabilities
Monetary items
US$000		7,867		29.9800		235,853
JPY000		1,033,394		0.2760		285,217


	December 31, 2020
	Foreign currency		Exchange rate		Carrying amount (NT$000)
(Foreign currency: functional currency)
Financial assets
Monetary items
US$000		175,840		28.4800		5,007,923
JPY000		137,635		0.2763		38,029
RMB000		6,838		4.3770		29,930
Non-monetary items
JPY000		948,270		0.2763		262,007
RMB000		690,178		4.3770		3,020,908
Financial liabilities
Monetary items
US$000		26,410		28.4800		752,157
JPY000		1,538,241		0.2763		425,016

The total exchange gains (losses), including realized and unrealized gains (losses) arising from significant foreign exchange variations on monetary items held by the Group for the years ended December 31, 2018, 2019 and 2020, amounted to gain of NT$93,104 thousand, loss of NT$154,993 thousand and loss of NT$355,255 thousand, respectively.

Analysis of foreign currency market risk arising from significant foreign exchange variations:


	Year ended December 31, 2018
	Sensitivity analysis
	Change in exchange rate			Effect on profit (loss) (NT$000)		Effect on other comprehensive income (NT$000)
Financial assets
Monetary items
US$000		5	%		261,492		—
JPY000		5	%		2,470		—
RMB000		5	%		1,979		—
Financial liabilities
Monetary items
US$000		5	%		27,997		—
JPY000		5	%		33,887		—


	Year ended December 31, 2019
	Sensitivity analysis
	Change in exchange rate			Effect on profit (loss) (NT$000)		Effect on other comprehensive income (NT$000)
Financial assets
Monetary items
US$000		5	%		282,365		—
JPY000		5	%		3,682		—
RMB000		5	%		1,334		—
Financial liabilities
Monetary items
US$000		5	%		11,793		—
JPY000		5	%		14,261		—


	Year ended December 31, 2020
	Sensitivity analysis
	Change in exchange rate			Effect on profit (loss) (NT$000)		Effect on other comprehensive income (NT$000)
Financial assets
Monetary items
US$000		5	%		250,396		—
JPY000		5	%		1,901		—
RMB000		5	%		1,497		—
Financial liabilities
Monetary items
US$000		5	%		37,608		—
JPY000		5	%		21,251		—

Price risk

The Group’s financial instruments, which are exposed to price risk, are the financial assets at fair value through profit or loss and financial assets at fair value through other comprehensive income. To manage its price risk arising from investments in financial instruments, the Group diversifies its portfolio. Diversification of the portfolio is in accordance with the limits set by the Group.

The Group invests in beneficiary certificates and listed stocks issued by the domestic companies. The prices of equity securities would change due to change of the future value of investee companies. For the years ended December 31, 2018, 2019 and 2020, it is estimated that the prices of equity securities increase or decrease by 1%, with all other variables held constant, would increase or decrease the Group’s profit before income tax by nil, nil and NT$531 thousand, respectively.

The Group’s investments in financial instruments comprise foreign unlisted stocks and partnership. The prices of financial instruments would change due to different valuation models and assumptions used. Analysis related to the effect on profit or other comprehensive income if these assumptions change is provided in Note 42 b) (g).

Interest rate risk on cash flow and fair value

Interest rate risk is the risk that the fair value or future cash flows of a financial instrument will fluctuate because of changes in market interest rates. The Group’s exposure to the risk of changes in market interest rates relates primarily to the Group’s bank loans with floating interest rates. The Group manages its interest rate risk by having a balanced portfolio of fixed and variable rate bank loans. The Group reassesses the hedge management periodically to make sure it complies with the cost effectiveness.

The sensitivity analysis depends on the exposure of interest rate risk at the end of the reporting period.

Analysis of debt with floating interest rates is based on the assumption that the outstanding debt at the end of the reporting period is outstanding throughout the period. The degree of variation the Group used to report to internal management is increase or decrease of 1% in interest rates which is assessed as the reasonable degree of variation by the management.

For the years ended December 31, 2018, 2019 and 2020, it is estimated that a general increase or decrease of 1% in interest rates, with all other variables held constant, would decrease or increase the Group’s profit before income tax approximately by NT$98,220 thousand, NT$90,660 thousand and NT$78,150 thousand, respectively, mainly due to the Group’s floating rate on bank loans.

ii)

Credit risk

Credit risk is the risk that a counterparty will not meet its obligations under a financial instrument or customer contract, leading to a financial loss, mainly resulted from its operating activities (primarily notes and accounts receivable) and from its financing activities (primarily deposits with banks and financial instruments). The Group is exposed to credit risk arising from the carrying amount of the financial assets recognized in the consolidated statements of financial position.

Each business unit performs ongoing credit evaluations of its debtors’ financial conditions according to the Group’s established policies, procedures and controls relating to customer credit risk management. The Group maintains an account for loss allowance based upon the available facts and circumstances, history of collection and

write-off

experiences of all trade and other receivables which consequently minimize the Group’s exposure to bad debts.

Credit risk from balances with banks and financial institutions is managed by the Group’s finance unit in accordance with the Group’s policies. Transaction counterparty of the Group is determined through its internal controls policy. For banks and financial institutions, only parties rated above BBB+ by Taiwan Ratings are accepted. The probability of counterparty default is remote, so there is no significant credit risk.

The Group adopts the assumptions under IFRS 9 “Financial Instruments” and the default is deemed to have occurred when the contract payments are past due over 90 days.

The Group categorized contract assets, accounts receivable and other receivables by characteristics of credit risk and applied the simplified approach using loss rate methodology to estimate expected credit loss.

The Group referred to the forecastability of business monitoring indicators published by the ROC National Development Council to adjust the loss rate which is based on historical and current information when assessing the future default possibility of contract assets, accounts receivable and other receivables. As of December 31, 2019 and 2020 the loss rate methodologies are as follows:


	December 31, 2019
	Contract assets			Accounts receivable (including related parties)			Other receivables (including related parties)
	NT$000			NT$000			NT$000
Expected loss rate		0.030	%		0.030	%		0.030	%
Total carrying amount		377,983			4,455,300			92,642
Loss allowance		(114	)		(1,351	)		(18	)


	December 31, 2020
	Contract assets			Accounts receivable (including related parties)			Other receivables (including related parties)
	NT$000			NT$000			NT$000
Expected loss rate		0.030	%		0.030	%		0.030	%
Total carrying amount		389,133			5,365,776			51,446
Loss allowance		(117	)		(1,620	)		(10	)

Under the simplified approach, movements in relation to loss allowance for contract assets, accounts receivable, and other receivables are as follows:


	2018
	Contract assets			Accounts receivable (including related parties)			Other receivables (including related parties)
	NT$000			NT$000			NT$000
January 1_ IAS 39		—			—			—
Adjustments for applying new standards		(115	)		(1,819	)		(7	)

January 1_IFRS 9		(115	)		(1,819	)		(7	)
Provision for impairment loss		(20	)		(322	)		(7	)
Reversal of impairment loss		—			—			1

December 31		(135	)		(2,141	)		(13	)


	2019
	Contract assets			Accounts receivable (including related parties)			Other receivables (including related parties)
	NT$000			NT$000			NT$000
January 1		(135	)		(2,141	)		(13	)
Provision for impairment loss		—			—			(5	)
Reversal of impairment loss		21			790			—

December 31		(114	)		(1,351	)		(18	)


	2020
	Contract assets			Accounts receivable (including related parties)			Other receivables (including related parties)
	NT$000			NT$000			NT$000
January 1		(114	)		(1,351	)		(18	)
Provision for impairment loss		(3	)		(269	)		—
Reversal of impairment loss		—			—			8

December 31		(117	)		(1,620	)		(10	)

The Group’s recorded financial assets at amortized cost include time deposits with contract period over three months and restricted bank deposits. Because of the low credit risk, expected credit losses for the period are measured through a loss allowance at an amount equal to the

12-month

expected credit losses. There is no significant provision for the losses.

iii)

Liquidity risk

The Group manages and maintains adequate cash and cash equivalents to finance the Group’s operations, and minimize the impact from cash flow fluctuations. The Group also monitors its debt financing plans to ensure it is in compliance with the financial covenants required under its loan agreements.

The primary source of liquidity for the Group is from bank loans. See Note 17 for details of the unused credit lines of the Group as of December 31, 2019 and 2020.

The contractual undiscounted cash flows of accounts payable and other payables due within one year and is equivalent to their carrying amounts. Except for the aforementioned, the table below summarizes the maturity profile of the Group’s

non-derivative

financial liabilities based on the earliest repayment dates and contractual undiscounted payments, including principal and interest. The Group does not consider the probability of early repayments requested by the banks.


	December 31, 2019
	Within 1 year		1 to 3 years		3 to 5 years		Over 5 years		Total
	NT$000		NT$000		NT$000		NT$000		NT$000
Non-derivative financial liabilities
Long-term bank loans		914,159		1,786,842		6,848,327		—		9,549,328
Lease liabilities		36,806		60,111		57,836		762,699		917,452
Guarantee deposits		—		—		—		1,095		1,095

		950,965		1,846,953		6,906,163		763,794		10,467,875


	December 31, 2020
	Within 1 year		1 to 3 years		3 to 5 years		Over 5 years		Total
	NT$000		NT$000		NT$000		NT$000		NT$000
Non-derivative financial liabilities
Long-term bank loans		846,401		3,558,597		2,198,717		1,487,808		8,091,523
Lease liabilities		145,594		160,146		54,689		718,752		1,079,181
Guarantee deposits		—		—		—		21,670		21,670

		991,995		3,718,743		2,253,406		2,228,230		9,192,374

The difference between the floating interest rates and estimated interest rates will affect the

non-derivative

financial liabilities stated above.

Fair value information

(a)

The different levels of inputs used in valuation techniques to measure fair value of financial and

non-financial

instruments are defined as follows:


Level 1:		Quoted prices (unadjusted) in active markets for identical assets or liabilities that can be accessed at the measurement date. An active market is a market in which trading for the asset or liability take place with sufficient frequency and volume to provide pricing information on an ongoing basis.

Level 2:		Inputs other than quoted prices from Level 1 that are observable information for the asset or liability, either directly or indirectly.

Level 3:		Unobservable inputs for the asset or liability. The fair value of the Group’s investment in equity investment without active market is included in Level 3.

(b)

The carrying amounts of cash and cash equivalents, financial assets at amortized cost, contract assets, notes receivable, accounts receivable (including related parties) , other receivables (including related parties), refundable deposits, long-term bank loans, contract liabilities, notes payable, accounts payable, other payables, lease liabilities and guarantee deposits are approximate to their fair values.

(c)

The related information of financial and

non-financial

instruments measured at fair value by level on the basis of the nature, characteristics and risks of the assets and liabilities are as follows:

The related information of natures of the assets and liabilities is as follows:


	December 31, 2019
	Level 1		Level 2		Level 3		Total
	NT$000		NT$000		NT$000		NT$000
Assets
Recurring fair value measurements
Financial assets at fair value through profit or loss
- Foreign partnership interests		—		—		11,038		11,038
Financial assets at fair value through other comprehensive income
- Foreign unlisted stocks		—		—		121,808		121,808

		—		—		132,846		132,846


	December 31, 2020
	Level 1		Level 2		Level 3		Total
	NT$000		NT$000		NT$000		NT$000
Assets
Recurring fair value measurements
Financial assets at fair value through profit or loss
- Listed stocks		53,120		—		—		53,120
- Foreign partnership interests		—		—		10,368		10,368
Financial assets at fair value through other comprehensive income
- Foreign unlisted stocks		—		—		262,007		262,007

		53,120		—		272,375		325,495

ii)

The methods and assumptions the Group used to measure fair value are as follows:

The fair value of the Group’s listed stocks is measured by using the market quoted prices, which is categorized within Level 1 fair value.

Except for listed stocks with active markets, the fair value of the Group’s other financial instruments is measured by using valuation techniques or by reference to counterparty quotes. The fair value of financial instruments measured by using valuation techniques can be referred to current fair value of instruments with similar terms and characteristics in substance, discounted cash flow method or other valuation methods, including calculated by applying model using market information available at the consolidated statement of financial position date.

The Group’s financial instruments issued by foreign partnerships are measured by using the discounted cash flow method, which derives present values estimates by discounting expected future operating effectiveness and free cash flow projections.

The Group’s financial instruments issued by foreign companies are measured by the comparable company valuation (EV/EBITDA ratio and P/B ratio).

The Group takes into account adjustments for credit risks to measure the fair value of financial and

non-financial

instruments to reflect credit risk of the counterparty and the Group’s credit quality.

(d)

The following table shows the movements of Level 3 for the years ended December 31, 2019 and 2020:


	December 31, 2019
	Debt instruments			Equity instruments			Total
	NT$000			NT$000			NT$000
January 1		11,471			174,357			185,828
Gains or losses recognized in profit or loss
Recorded as non-operating expenses		(433	)		—			(433	)
Gains or losses recognized in other comprehensive income
Recorded as unrealized losses on valuation of financial assets at fair value through other comprehensive income		—			(52,549	)		(52,549	)

December 31		11,038			121,808			132,846


	December 31, 2020
	Debt instruments			Equity instruments		Total
	NT$000			NT$000		NT$000
January 1		11,038			121,808		132,846
Gains or losses recognized in profit or loss
Recorded as non-operating expenses		(670	)		—		(670	)
Gains or losses recognized in other comprehensive income
Recorded as unrealized gains on valuation of financial assets at fair value through other comprehensive income		—			140,199		140,199

December 31		10,368			262,007		272,375

(e)

The Group performs the fair value measurements being categorized within Level 3 with assistance from specialist. Such assessment is to ensure the valuation results are reasonable by applying independent information to make results close to current market conditions, confirming the resource of information is independent, reliable and in line with other resources and represented as the exercisable price, and frequently calibrating valuation model, updating inputs used to the valuation model and making any other necessary adjustments to the fair value.

(f)

The following is the qualitative information and sensitivity analysis of changes in significant unobservable inputs under valuation model used in Level 3 fair value measurement:

Fair value as of

December 31,
2019

Valuation

technique

Significant

unobservable
input

Range

(weighted

average
method)

Relationship of inputs

to fair value

NT$000

Non-derivative

debt instrument:

Foreign partnership interests

11,038

Discounted cash flow

Discount
rate

0.30

The lower the discount rate, the higher the fair value

Non-derivative

equity instrument:

Foreign unlisted stocks

121,808

Comparable

companies

Price to book
ratio
multiple

1.22

The higher the multiple, the higher the fair value

Enterprise
value to
EBITDA
multiple

10.51

The higher the multiple, the higher the fair value

Discount for
lack of
marketability

15.80

The higher the discount for lack of marketability, the lower the fair value

Fair value as of

December 31,
2020

Valuation

technique

Significant

unobservable
input

Range

(weighted

average
method)

Relationship of inputs

to fair value

NT$000

Non-derivative

debt instrument:

Foreign partnership interests

10,368

Discounted cash flow

Discount
rate

0.30

The lower the discount rate, the higher the fair value

Non-derivative

equity instrument:

Foreign unlisted stocks

262,007

Comparable

companies

Price to book
ratio
multiple

1.97

The higher the multiple, the higher the fair value

Enterprise
value to
EBITDA
multiple

12.00

The higher the multiple, the higher the fair value

Discount for
lack of
marketability

15.80

The higher the discount for lack of marketability, the lower the fair value

(g)

The Group has carefully assessed the valuation models and assumptions used to measure fair value. However, use of different valuation models or assumptions may result in different measurement. The following is the effect of profit or loss or of other comprehensive income from financial assets categorized within Level 3 if the inputs used to valuation models have changed:


			December 31, 2019
			Recognized in profit or loss				Recognized in other comprehensive income
	Input	Change	Favorable change		Unfavorable change		Favorable change		Unfavorable change
			NT$000		NT$000		NT$000		NT$000
Financial assets:
Foreign partnership interests	Discount rate	Note		—		—		—		—
Foreign unlisted stocks	Price to book ratio multiple	± 1%		—		—		53		53
	Enterprise value to EBITDA multiple	± 1%		—		—		850		900
	Discount for lack of marketability	± 1%		—		—		1,460		1,460

				—		—		2,363		2,413


						December 31, 2020
						Recognized in profit or loss				Recognized in other comprehensive income
	Input		Change			Favorable change		Unfavorable change		Favorable change		Unfavorable change
						NT$000		NT$000		NT$000		NT$000
Financial assets:
Foreign partnership interests		Discount rate		Note			—		—		—		—
Foreign unlisted stocks		Price to book ratio multiple		± 1	%		—		—		30		30
		Enterprise value to EBITDA multiple		± 1	%		—		—		2,153		2,153
		Discount for lack of marketability		± 1	%		—		—		3,142		3,084

							—		—		5,325		5,267

Note:

Based on the Group’s assessment, change in input would not have significant impact on profit or loss or other comprehensive income.

Segment Information

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Segment Information

43.	Segment Information

General information

The Group engages mainly in the assembly and testing of semiconductors, memory modules and general investments. In accordance with IFRS 8 “Operating Segments”, the Group’s segments include Testing, Assembly, Testing and Assembly for LCD, OLED and other Display Panel Driver Semiconductors (“LCDD”), Bumping and others as the five reportable segments.

Measurement of segment information

The Group’s reportable segments are strategic business units which provide different products and services. The accounting policies adopted by the operating segments are the same as the accounting policies described in Note 4.

Information about segment profit or loss

The segment information provided to the chief operating decision maker for the reportable segments is as follows:


	Year ended December 31, 2018
	Testing			Assembly			LCDD			Bumping			Others			Elimination			Total
	NT$000			NT$000			NT$000			NT$000			NT$000			NT$000			NT$000
Revenue
External customers		4,790,097			4,679,676			5,694,720			3,315,534			—			—			18,480,027
Inter-segment		—			—			—			—			35,738			(35,738	)		—

Total revenue		4,790,097			4,679,676			5,694,720			3,315,534			35,738			(35,738	)		18,480,027

Operating profit (loss)		1,306,742			(207,700	)		1,226,755			(202,497	)		(23,433	)		(146	)		2,099,721

Depreciation expenses		(769,660	)		(578,205	)		(1,400,784	)		(627,412	)		(518	)		—			(3,376,579	)

Share of profit (loss) of associates		—			—			—			—			(668,377	)		368,276			(300,101	)

Interest income		—			—			—			—			49,971			—			49,971

Interest expense		—			—			—			—			(152,416	)		—			(152,416	)

Purchase of property, plant and equipment		1,563,919			321,976			2,732,141			327,251			283			—			4,945,570


	Year ended December 31, 2019
	Testing			Assembly			LCDD			Bumping			Others			Elimination			Total
	NT$000			NT$000			NT$000			NT$000			NT$000			NT$000			NT$000
Revenue
External customers		4,257,800			5,148,877			6,922,205			4,008,999			—			—			20,337,881
Inter-segment		—			—			—			—			32,808			(32,808	)		—

Total revenue		4,257,800			5,148,877			6,922,205			4,008,999			32,808			(32,808	)		20,337,881

Operating profit (loss)		709,142			(227,096	)		1,740,720			232,404			1,931			18			2,457,119

Depreciation expenses		(802,740	)		(521,311	)		(1,796,951	)		(604,553	)		(6,359	)		—			(3,731,914	)

Share of profit (loss) of associates		—			—			—			—			(370,351	)		215,425			(154,926	)

Interest income		—			—			—			—			64,368			—			64,368

Interest expense		—			—			—			—			(171,075	)		—			(171,075	)

Purchase of property, plant and equipment		764,105			548,063			3,077,806			506,635			47			—			4,896,656


	Year ended December 31, 2020
	Testing			Assembly			LCDD			Bumping			Others			Elimination			Total
	NT$000			NT$000			NT$000			NT$000			NT$000			NT$000			NT$000
Revenue
External customers		5,002,730			6,001,964			7,023,003			4,983,684			—			—			23,011,381
Inter-segment		—			—			—			—			39,646			(39,646	)		—

Total revenue		5,002,730			6,001,964			7,023,003			4,983,684			39,646			(39,646	)		23,011,381

Operating profit (loss)		1,333,682			67,730			1,687,986			487,323			(10,230	)		11			3,566,502

Depreciation expenses		(853,829	)		(523,341	)		(2,213,504	)		(578,890	)		(5,955	)		—			(4,175,519	)

Share of profit (loss) of associates		—			—			—			—			(320,578	)		173,249			(147,329	)

Interest income		—			—			—			—			27,778			—			27,778

Interest expense		—			—			—			—			(162,400	)		—			(162,400	)

Purchase of property, plant and equipment		887,204			803,693			2,143,401			298,834			483			—			4,133,615

Reconciliation for segment income (loss)

Revenue from external customers and segment income (loss) reported to the chief operating decision maker are measured using the same method as for revenue and operating profit in the financial statements. Thus, no reconciliation is needed.

Information on products and services


	Year ended December 31,
	2018				2019				2020
	NT$000		%		NT$000		%		NT$000		%
Testing		4,790,097		26		4,257,800		21		5,002,730		22
Assembly		4,679,676		25		5,148,877		25		6,001,964		26
LCDD		5,694,720		31		6,922,205		34		7,023,003		30
Bumping		3,315,534		18		4,008,999		20		4,983,684		22

		18,480,027		100		20,337,881		100		23,011,381		100

Geographical information


	Year ended December 31,
	2018		2019		2020
	NT$000		NT$000		NT$000
Revenue
ROC		14,751,766		15,875,027		18,341,726
Japan		1,825,479		1,905,032		1,291,026
Singapore		1,143,661		1,333,114		1,838,394
PRC		163,831		789,496		1,105,535
Others		595,290		435,212		434,700

		18,480,027		20,337,881		23,011,381


	December 31, 2019		December 31, 2020
	NT$000		NT$000
Non-current assets
ROC		18,727,979		18,913,501
PRC		—		117
Others		5,659		11,845

		18,733,638		18,925,463

Major customer information

The information on the major customers which constituted more than 10% of the Group’s total revenue for the years ended December 31, 2018, 2019 and 2020 is as follows:


	Year ended December 31,
	2018				2019				2020
	Amount		%		Amount		%		Amount		%
	NT$000				NT$000				NT$000
Customers
Customer A		3,794,991		21		4,756,755		23		5,088,544		22
Customer X		1,328,752		7		1,977,427		10		2,660,866		12
Customer K		2,637,053		14		2,419,612		12		2,332,914		10
Customer C		1,957,467		11		2,048,260		10		2,143,130		9

Financial Statements Schedule: Valuation and Qualifying Accounts

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Financial Statements Schedule: Valuation and Qualifying Accounts

44.	Financial Statements Schedule: Valuation and Qualifying Accounts


	January 1		Additions charged to expense or deduction of revenue		Deduction / Write-offs / Reversal			December 31
	NT$000		NT$000		NT$000			NT$000
Year of 2018 :
Allowance for impairment of property, plant and equipment		320,455		—		(2,862	)		317,593
Allowance for impairment of obsolescence and decline in market value of inventories		53,714		—		(17,557	)		36,157
Provision for deficiency compensation		57,155		14,211		(42,014	)		29,352
Sales for allowance		70,156		44,950		(82,479	)		32,627
Year of 2019 :
Allowance for impairment of property, plant and equipment		317,593		9,938		(134,191	)		193,340
Allowance for impairment of obsolescence and decline in market value of inventories		36,157		27,341		—			63,498
Provision for deficiency compensation		29,352		5,204		(32,558	)		1,998
Sales for allowance		32,627		63,863		(70,490	)		26,000
Year of 2020 :
Allowance for impairment of property, plant and equipment		193,340		—		(11,338	)		182,002
Allowance for impairment of obsolescence and decline in market value of inventories		63,498		16,317		—			79,815
Provision for deficiency compensation		1,998		4,358		(2,893	)		3,463
Sales for allowance		26,000		21,916		(38,052	)		9,864

For movements in loss allowance for contract assets, accounts receivable, and other receivables, please refer to Note 42.

Effects on initial application of IFRS 16

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Effects on initial application of IFRS 16

45.	Effects on initial application of IFRS 16

IFRS 16, supersedes IAS 17 “Leases” (“IAS 17”) and the related interpretations issued by the Standing Interpretation Committee. The standard requires lessees to recognize a

right-of-use

asset and a lease liability (except for those leases with terms of 12 months or less and leases of

low-value

assets). The accounting stays the same for lessors, which is to classify their leases as either finance leases or operating leases and account for those two types of leases differently. IFRS 16 only requires enhanced disclosures to be provided by lessors.

The Group has elected to apply IFRS 16 by not restating the comparative information (referred herein as the “simplified retrospective approach”) when applying IFRSs effective in 2019. Accordingly, the Group increased

right-of-use

assets and lease liabilities by NT$898,387 thousand and NT$884,275 thousand, respectively, and decreased leased assets and lease obligations payable by NT$31,904 thousand and NT$17,792 thousand, respectively.

The Group has adopted the following practical expedients permitted by the standard at the date of initial application of IFRS 16:

(a)

Reassessment as to whether a contract is, or contains, a lease is not required, instead, the application of IFRS 16 depends on whether or not the contracts were previously identified as leases applying IAS 17 and IFRIC 4 “Determining whether an Arrangement contains a Lease”.

(b)

The use of a single discount rate to a portfolio of leases with reasonably similar characteristics.

(c)

The accounting for operating leases whose period will end before December 31, 2019 as short-term leases and accordingly, rent expense of NT$28,126 thousand was recognized for the year ended 2019.

The Group calculated the present value of lease liabilities by using the incremental borrowing interest rate, ranging from 1.7895% to 3.9474%.

The reconciliation between operating lease commitments for the remaining lease payments under IAS 17 and lease liabilities recognized as of January 1, 2019, measured at the present value of the remaining lease payments, discounted using the lessee’s incremental borrowing rate is as follows:


	NT$000
Operating lease commitments disclosed by applying IAS 17 as of December 31, 2018		320,214
Add: Lease payable recognized under finance lease by applying IAS 17 as of December 31, 2018		17,792
Less: Short-term leases		(28,121	)
Add: Adjustments as a result of a different treatment of extension and termination options		874,298

Total lease contracts amount recognized as lease liabilities by applying IFRS 16 on January 1, 2019		1,184,183

Incremental borrowing interest rate at the date of initial application		1.7895%~3.9474	%

Lease liabilities recognized as of January 1, 2019 by applying IFRS 16		884,275

Effects on initial application of IFRS 9

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Effects on initial application of IFRS 9

46.	Effects on initial application of IFRS 9

Impact on January 1, 2018

The Group initially applied IFRS 9 on January 1, 2018, and recorded loss allowance based on expected credit loss. The impact was contract assets decreased by NT$115 thousand, accounts receivable decreased by NT$1,819 thousand, other receivables decreased by NT$5 thousand, other receivables

—

related parties decreased by NT$2 thousand, retained earnings decreased by NT$1,940 thousand and deferred tax assets increased by NT$1 thousand.

The carrying amount of financial assets transferred from December 31, 2017 under IAS 39 to January 1, 2018 under IFRS 9 is reconciled as follows:


																	Effects
	Note		Measured at cost			Measured at fair value through profit or loss		Measured at fair value through other comprehensive income		Other financial assets			Measured at amortized cost		Total		Retained earnings		Other equity interest
			NT$000			NT$000		NT$000		NT$000			NT$000		NT$000		NT$000		NT$000
IAS 39				20,890			—		—		70,241			—		91,131		—		—
Transferred into and measured at fair value through profit or loss		(c)		(10,940	)		10,940		—		—			—		—		—		—
Transferred into and measured at fair value through other comprehensive income		(b)		(9,950	)		—		9,950		—			—		—		—		—
Transfer into and measured at amortized cost		(a)		—			—		—		(70,241	)		70,241		—		—		—
Fair value adjustment		(b)(c)		—			493		50,801		—			—		51,294		493		79,385
Impairment loss adjustment		(b)		—			—		28,584		—			—		28,584		28,584		(28,584	)
Income tax adjustment		(b)		—			—		—		—			—		—		—		(8,636	)

IFRS 9				—			11,433		89,335		—			70,241		171,009		29,077		42,165

(a)

The Group’s restricted bank deposits that failed to meet the definition of cash and cash equivalents amounted to NT$70,241 thousand were classified as “Other financial assets” under IAS 39. Since the assets’ cash flows represent solely payments of principal and interest, the restricted bank deposits were reclassified as “Financial assets at amortized cost” amounted to NT$70,241 thousand on initial application of IFRS 9.

(b)

Given the Group’s

available-for-sale

financial assets amounted to NT$9,950 thousand under IAS 39 were not held for the purpose of trading, it was elected to classify as “Financial assets at fair value through other comprehensive income” and increased by NT$89,335 thousand on initial application of IFRS 9. Accompanying retained earnings, other equity interest and deferred tax liabilities were increased by NT$28,584 thousand, NT$42,165 thousand and NT$8,636 thousand, respectively.

(c)

The Group’s

available-for-sale

financial assets amounted to NT$10,940 thousand under IAS 39 were classified as “Financial assets at fair value through profit or loss” and increased by NT$11,433 thousand in compliance with IFRS 9. Accompanying retained earnings were increased by NT$493 thousand.

Effects of initial application of IFRS 15

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Effects of initial application of IFRS 15

47.	Effects of initial application of IFRS 15

Impact on January

1, 2018

Revenue recognition of customized products

The Group provides high-integration and high-precision integrated circuits and related assembly and testing services based on the specifications as required by the customers. The revenue is recognized when the significant risks and rewards are transferred to customers under previous accounting policies, and the timing of recognition usually occurred upon service completion. Under IFRS 15, considering that the Group provides assembly and testing service to create or enhance a highly customized product and the customer controls the asset as it is created or enhanced, the revenue will be recognized based on the progress towards completion. As a result, retained earnings increased by NT$46,607 thousand, inventories decreased by NT$208,505 thousand and contract assets increased by NT$255,112 thousand.

Presentation of refund liabilities

By adopting IFRS 15, the Group’s provision for sales allowance amounted to NT$70,156 thousand is presented as current refund liabilities from January 1, 2018, which was previously presented as current provisions.

Recognition of deferred tax

When initially adopting IFRS 15, the Group recognized adjustments in the statement of financial position which resulted to temporary differences. Accordingly, as of January 1, 2018, deferred tax assets decreased by NT$626 thousand, deferred tax liabilities increased by NT$8,067 thousand and retained earnings decreased by NT$8,693 thousand.

Summary of significant accounting policies (Policies)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Statement of compliance

The consolidated financial statements of the Group have been prepared in accordance with IFRSs as issued by the IASB.

Basis of preparation

(a)

Except for the following items, the consolidated financial statements have been prepared under the historical cost convention:

Financial assets at fair value through profit or loss (including derivative instruments).

ii)

Financial assets at fair value through other comprehensive income.

iii)

Defined benefit liabilities were recognized based on the net amount of pension fund assets less the present value of benefit obligation.

(b)

(c)

These consolidated financial statements are presented in New Taiwan dollars (“NT$”), which is the Company’s functional currency.

(d)

Basis of consolidation

(a)

Basis for preparation of consolidated financial statements:

ii)

iii)

Profit or loss and each component of other comprehensive income are attributed to the owners of the parent and to the

non-controlling

interests. Total comprehensive income is attributed to the owners of the parent and to the

non-controlling

interests even if this results in a deficit balance in the

non-controlling

interests.

iv)

Changes in a parent’s ownership interest in a subsidiary that do not result in the parent losing control of the subsidiary (transactions with

non-controlling

interests) are accounted for as equity transactions, i.e. transactions with owners in their capacity as owners. Any difference between the amount by which the

non-controlling

interests are adjusted and the fair value of the consideration paid or received is recognized directly in equity.

(b)

Subsidiaries included in the consolidated financial statements:

Percentage of

Ownership (%)

December 31,

Name of investor

Name of investee

Main business

Location

2019

2020

Note

The Company

ChipMOS U.S.A., Inc.
(“ChipMOS USA”)

Marketing of semiconductors and electronic related products

San Jose, USA

100

The Company

ChipMOS
TECHNOLOGIES
(BVI) LTD.

(“ChipMOS BVI”)

Holding company

British Virgin
Islands

100

ChipMOS BVI

ChipMOS
SEMICONDUCTORS
(Shanghai) LTD.
(“ChipMOS
Shanghai”)

Marketing of semiconductors and electronic related products

Shanghai,
People’s
Republic of
China
(“PRC”)

—

100

Note

(c)

Subsidiaries not included in the consolidated financial statements: None.

(d)

Adjustments for subsidiaries with different statements of financial position dates: Not applicable.

(e)

No significant restrictions on the ability of subsidiaries to transfer funds to parent company.

(f)

Subsidiaries that have

non-controlling

interests that are material to the Group: None.

Foreign currency translation

(a)

Foreign currency transactions and balances

ii)

Monetary assets and liabilities denominated in foreign currencies at the period end are

re-translated

at the exchange rates prevailing at the statements of financial position date. Exchange differences arising upon

re-translation

are recognized in profit or loss on the statements of financial position date.

iii)

Non-monetary

assets and liabilities denominated in foreign currencies held at fair value through profit or loss are

re-translated

at the exchange rates prevailing at the statements of financial position date; their exchange differences are recognized in profit or loss.

Non-monetary

assets and liabilities denominated in foreign currencies held at fair value through other comprehensive income are

re-translated

at the exchange rates prevailing at the statements of financial position date; their exchange differences are recognized in other comprehensive income. However,

non-monetary

assets and liabilities denominated in foreign currencies that are not measured at fair value are translated using the historical exchange rates at the initial dates of the transactions.

iv)

All foreign exchange differences are presented in the statement of comprehensive income under “Other gains and losses” by the nature of transactions.

(b)

Translation of foreign operations

Assets and liabilities for each statements of financial position are translated at the exchange rates prevailing at the statements of financial position date;

ii)

Income and expenses for each statement of comprehensive income are translated at average exchange rates of that period; and

iii)

All exchange differences are recognized in other comprehensive income.

Classification of current and non-current assets and liabilities


	e)	Classification of current and non-current assets and liabilities

(a)

Assets that meet one of the following criteria are classified as current assets:

Assets arising from operating activities that are expected to be realized, or are intended to be sold or consumed within the normal operating cycle;

ii)

Assets held mainly for trading purposes;

iii)

Assets that are expected to be realized within 12 months from the statements of financial position date;

iv)

All assets that do not meet the above criteria are classified as

non-current

assets.

(b)

Liabilities that meet one of the following criteria are classified as current liabilities:

Liabilities that are expected to be settled within the normal operating cycle;

ii)

Liabilities arising mainly from trading activities;

iii)

Liabilities that are to be settled within 12 months from the statements of financial position date;

iv)

All liabilities that do not meet the above criteria are classified as

non-current

liabilities.

Cash equivalents

Financial assets at fair value through profit or loss

(a)

Financial assets at fair value through profit or loss are financial assets that are not measured at amortized cost or fair value through other comprehensive income.

(b)

On a regular way purchase or sale basis, financial assets at fair value through profit or loss are recognized and derecognized using settlement date accounting.

(c)

(d)

Financial assets at fair value through other comprehensive income

(a)

(b)

On a regular way purchase or sale basis, financial assets at fair value through other comprehensive income are recognized and derecognized using settlement date accounting.

(c)

At initial recognition, the Group measures the financial assets at fair value plus transaction costs. The Group subsequently measures the financial assets at fair value.

Financial assets at amortized cost

(a)

Financial assets at amortized cost are those that meet all of the following criteria:

The objective of the Group’s business model is achieved by collecting contractual cash flows.

ii)

The financial assets’ contractual cash flows represent solely payments of principal and interest.

(b)

The Group’s time deposits which do not fall under cash equivalents are those with a short maturity period and are measured at initial investment amount as the effect of discounting is immaterial.

Accounts and notes receivable

(a)

Accounts and notes receivable entitle the Group a legal right to receive consideration in exchange for transferred goods or rendered services.

(b)

The short-term accounts and notes receivable without bearing interest are subsequently measured at initial invoice amount as the effect of discounting is immaterial.

Impairment of financial assets

Derecognition of financial assets

The Group derecognizes a financial asset when the contractual rights to receive the cash flows from the financial asset have expired.

Inventories

Investments accounted for using equity method – associates

(a)

(b)

(c)

(d)

(e)

(f)

Property, plant and equipment

(a)

Property, plant and equipment are initially recorded at cost. Borrowing costs incurred during the construction period are capitalized.

(b)

(c)

(d)

The assets’ residual values, useful lives and depreciation methods are reviewed, and adjusted if appropriate, at each financial

year-end.


Buildings		5 to 51 years
Machinery and equipment		2 to 8 years
Tools		2 to 4 years
Others		2 to 6 years

Leasing arrangements (lessee) – right-of-use assets / lease liabilities

Leasing arrangements (lessee)

right-of-use

assets / lease liabilities

(a)

Leases are recognized as a

right-of-use

(b)

Lease liabilities include the net present value of the remaining lease payments at the commencement date, discounted using the incremental borrowing interest rate.

Lease payments are comprised of the following:

Fixed payments, less any lease incentives receivable;

ii)

The exercise price of a purchase option, if the lessee is reasonably certain to exercise that option.

right-of-use

asset when there are changes in the lease term or lease payments and such changes do not arise from contract modifications.

(c)

At the commencement date, the

right-of-use

asset is stated at the amount of the initial measurement of lease liability. The

right-of-use

asset.

Impairment of non-financial assets

Impairment of

non-financial

assets

Loans

Accounts and notes payable

(a)

Accounts payable are liabilities for purchases of raw materials, goods or services and notes payable are those resulting from operating and

non-operating

activities.

(b)

The short-term accounts and notes payable without bearing interest are subsequently measured at initial invoice amount as the effect of discounting is immaterial.

Derecognition of financial liabilities

A financial liability is derecognized when the obligation specified in the contract is either discharged or cancelled or expires.

Provisions for deficiency compensation

pre-tax

Employee benefits

(a)

Short-term employee benefits

(b)

Pensions

Defined contribution plans

ii)

Defined benefit plans

Remeasurements arising on defined benefit plans are recognized in other comprehensive income in the period in which they arise and are recorded as retained earnings.

Past service costs are recognized immediately in profit or loss.

(c)

Termination benefits

(d)

Employees’ compensation and directors’ remuneration

Employee share-based payments

Restricted shares

(a)

Restricted shares issued to employees are measured at the fair value of the equity instruments granted at the grant date, and are recognized as compensation cost over the vesting period.

(b)

(c)

For restricted shares where employees do not need to pay to acquire those shares, if an employee resigns during the vesting period, the Group will recover and retire those shares at no cost.

Income tax

(a)

(b)

(c)

(d)

(e)

(f)

Capital stock

(a)

Ordinary shares are classified as equity. Incremental costs directly attributable to the issue of new shares in net proceeds of tax are shown in equity as a deduction.

(b)

Dividends

Revenue recognition

aa)

Revenue recognition

(a)

Customer controls the provided raw materials and the Group receives the instruction from the customer on providing assembly and testing services and subsequent treatments.

ii)

The Group provides assembly and testing services to create or enhance an asset which is solely provided and controlled by the customer. The Group has no right to transfer the asset for another use.

(b)

Government grants

bb)

Government grants

non-current

liabilities and are amortized to profit or loss over the estimated useful lives of the related assets using straight-line method.

Operating segments

cc)

Operating segments

Critical accounting judgments, estimates and key sources of assumption uncertainty

dd)

Critical accounting judgments, estimates and key sources of assumption uncertainty

Critical accounting estimates and assumptions

—

Revenue recognition

Summary of significant accounting policies (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Ownership Interests in Subsidiaries

Percentage of

Ownership (%)

December 31,

Name of investor

Name of investee

Main business

Location

2019

2020

Note

The Company

ChipMOS U.S.A., Inc.
(“ChipMOS USA”)

Marketing of semiconductors and electronic related products

San Jose, USA

100

The Company

ChipMOS
TECHNOLOGIES
(BVI) LTD.

(“ChipMOS BVI”)

Holding company

British Virgin
Islands

100

ChipMOS BVI

ChipMOS
SEMICONDUCTORS
(Shanghai) LTD.
(“ChipMOS
Shanghai”)

Marketing of semiconductors and electronic related products

Shanghai,
People’s
Republic of
China
(“PRC”)

—

100

Note

Estimated Useful Life for Depreciation of Individual Assets


Buildings		5 to 51 years
Machinery and equipment		2 to 8 years
Tools		2 to 4 years
Others		2 to 6 years

Cash and cash equivalents (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Cash and Cash Equivalents


	December 31, 2019		December 31, 2020
	NT$000		NT$000
Cash on hand and petty cash		470		470
Checking accounts and demand deposits		915,134		2,609,421
Time deposits		3,788,480		1,503,760

		4,704,084		4,113,651

The Group transacts with a variety of financial institutions all with high credit quality to disperse credit risk, so it expects that the probability of counterparty default is remote.

No cash and cash equivalents of the Group were pledged to others.

Financial assets at fair value through profit or loss (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Financial Assets at Fair Value Through Profit or Loss


	December 31, 2019		December 31, 2020
	NT$000		NT$000
Current:
Financial assets mandatorily measured at fair value through profit or loss
Listed stocks		—		46,512
Valuation adjustment		—		6,608

		—		53,120

Non-current:
Financial assets mandatorily measured at fair value through profit or loss
Foreign partnership interests		10,940		10,940
Valuation adjustment		98		(572	)

		11,038		10,368

Summary of Amounts recognized in Profit or Loss in Relation to Financial Assets at Fair Value Through Profit or Loss

Amounts recognized in profit or loss in relation to the financial assets at fair value through profit or loss are listed below:


	Year ended December 31,
	2018		2019			2020
	NT$000		NT$000			NT$000
Financial assets mandatorily measured at fair value through profit or loss
Beneficiary certificates*		1,396		1,750			18,077
Listed stocks		—		—			6,608
Foreign partnership interests		38		(433	)		(670	)
Derivative instruments		51		—			—

		1,485		1,317			24,015

No financial assets at FVTPL were pledged to others.

Information relating to price risk of financial assets at FVTPL is provided in Note 42.

Financial assets at amortized cost (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Financial Assets at Amortized Cost


	December 31, 2019		December 31, 2020
	NT$000		NT$000
Current:
Time deposits		168,970		206,482

Non-current:
Restricted bank deposits		68,450		48,319

Amounts recognized in profit or loss in relation to financial assets at amortized cost are listed below:


	Year ended December 31,
	2018		2019		2020
	NT$000		NT$000		NT$000
Interest income		920		4,467		2,206

Accounts receivable (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Accounts and notes receivable


	December 31, 2019			December 31, 2020
	NT$000			NT$000
Accounts receivable		4,454,255			5,365,776
Less: Loss allowance		(1,351	)		(1,620	)

		4,452,904			5,364,156

Aging of Accounts Receivable which are Past Due but not Impaired


	December 31, 2019		December 31, 2020
	NT$000		NT$000
Current		4,440,081		5,272,208
Within 1 month		13,733		93,568
1 – 2 months		441		—

		4,454,255		5,365,776

Inventories (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Inventories

December 31, 2019

Cost

Allowance for
impairment losses

Carrying amount

NT$000

Raw materials

1,831,140

(63,498

)

1,767,642

December 31, 2020

Cost

Allowance for
impairment losses

Carrying amount

NT$000

Raw materials

2,181,890

(79,815

)

2,102,075

Cost of Inventories Recognized as an Expense

The cost of inventories recognized as an expense for the year:


	Year ended December 31,
	2018			2019		2020
	NT$000			NT$000		NT$000
Cost of revenue		15,057,605			16,372,032		17,957,568
Loss on abandonment		5,497			12,369		5,323
Allowance for (reversal of ) inventory valuation and obsolescence loss		(13,070	)		27,341		16,317

		15,050,032			16,411,742		17,979,208

Non-current financial assets at fair value through other comprehensive income (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Non-current Financial Assets at Fair Value Through Other Comprehensive Income


	December 31, 2019		December 31, 2020
	NT$000		NT$000
Designation of equity instruments
Foreign unlisted stocks		38,534		38,534
Valuation adjustment		83,274		223,473

		121,808		262,007

Summary Amounts recognized in other comprehensive income in relation to the financial assets at fair value through other comprehensive income

Amounts recognized in other comprehensive income in relation to the financial assets at fair value through other comprehensive income are listed below:


	Year ended December 31,
	2018		2019			2020
	NT$000		NT$000			NT$000
Financial assets at fair value through other comprehensive income
Foreign unlisted stocks		85,022		(52,549	)		140,199

Investments accounted for using equity method (Tables)

12 Months Ended

Dec. 31, 2020

Investments accounted for using equity method [abstract]

Details of Investment in Associates


	December 31, 2019		December 31, 2020
	NT$000		NT$000
JMC ELECTRONICS CO., LTD. (“JMC”)		249,793		250,769
Unimos Microelectronics (Shanghai) Co., Ltd. (“Unimos Shanghai”)		3,143,117		3,020,908

		3,392,910		3,271,677


		Shareholding ratio
Company name	Principal place of business	December 31, 2019	December 31, 2020	Nature of relationship	Method of measurement
Unimos Shanghai	Shanghai, PRC	45.02%	45.02%	Strategic Investee	Equity method

Summarized Financial Information for Investment in Material Associates

Statement of financial position


	Unimos Shanghai
	December 31, 2019			December 31, 2020
	NT$000			NT$000
Current assets		3,042,377			2,438,725
Non-current assets		3,499,819			3,905,089
Current liabilities		(459,502	)		(618,949	)
Non-current liabilities		(448,929	)		(248,583	)

Total net assets		5,633,765			5,476,282

Share in associate’s net assets		2,536,558			2,465,651
Depreciable assets		584,441			533,139
Goodwill		22,118			22,118

Carrying amount of the associate		3,143,117			3,020,908

Statement of comprehensive income


	Unimos Shanghai
	Year ended December 31,
	2018			2019			2020
	NT$000			NT$000			NT$000
Revenue		1,334,196			1,584,648			1,739,880

Loss for the year from continuing operations		(629,303	)		(352,008	)		(246,220	)
Other comprehensive income, net of income tax		—			—			—

Total comprehensive loss		(629,303	)		(352,008	)		(246,220	)

Dividends received from the associate		—			—			—


	Year ended December 31,
	2018			2019		2020
	NT$000			NT$000		NT$000
Profit for the year from continuing operations		41,933			63,838		14,833
Other comprehensive (loss) income, net of income tax		(2,687	)		5,732		23,143

Total comprehensive income		39,246			69,570		37,976

Property, plant and equipment, net (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Property, Plant and Equipment, Net


	2018
	Land		Buildings			Machinery and equipment			Tools			Others			Construction in progress and equipment to be inspected			Total
	NT$000		NT$000			NT$000			NT$000			NT$000			NT$000			NT$000
January 1
Cost		452,738		9,809,970			45,778,207			4,004,703			2,624,083			968,719			63,638,420
Accumulated depreciation and impairment		—		(5,890,884	)		(36,964,480	)		(3,314,234	)		(2,203,511	)		—			(48,373,109	)

		452,738		3,919,086			8,813,727			690,469			420,572			968,719			15,265,311

January 1		452,738		3,919,086			8,813,727			690,469			420,572			968,719			15,265,311
Additions		—		247,186			2,445,313			591,229			172,652			1,489,190			4,945,570
Disposals		—		—			(904	)		(11,745	)		(2,067	)		—			(14,716	)
Reclassifications		—		199,724			1,154,663			7,604			26,026			(1,388,017	)		—
Depreciation expenses		—		(457,265	)		(2,180,718	)		(535,378	)		(203,218	)		—			(3,376,579	)
Exchange adjustment		—		—			12			—			23			—			35

December 31		452,738		3,908,731			10,232,093			742,179			413,988			1,069,892			16,819,621

December 31
Cost		452,738		10,254,531			48,274,171			4,402,711			2,610,893			1,069,892			67,064,936
Accumulated depreciation and impairment		—		(6,345,800	)		(38,042,078	)		(3,660,532	)		(2,196,905	)		—			(50,245,315	)

		452,738		3,908,731			10,232,093			742,179			413,988			1,069,892			16,819,621


	2019
	Land		Buildings			Machinery and equipment			Tools			Others			Construction in progress and equipment to be inspected			Total
	NT$000		NT$000			NT$000			NT$000			NT$000			NT$000			NT$000
January 1
Cost		452,738		10,254,531			48,274,171			4,402,711			2,610,893			1,069,892			67,064,936
Accumulated depreciation and impairment		—		(6,345,800	)		(38,042,078	)		(3,660,532	)		(2,196,905	)		—			(50,245,315	)

		452,738		3,908,731			10,232,093			742,179			413,988			1,069,892			16,819,621

January 1		452,738		3,908,731			10,232,093			742,179			413,988			1,069,892			16,819,621
Effects on initial application of IFRS 16		—		—			—			—			(31,904	)		—			(31,904	)

Adjusted balance at January 1		452,738		3,908,731			10,232,093			742,179			382,084			1,069,892			16,787,717
Additions		—		116,238			2,334,358			781,465			224,287			1,440,308			4,896,656
Disposals		—		—			(16,033	)		(9,336	)		(416	)		—			(25,785	)
Reclassifications		—		455,792			1,111,715			7,880			25,042			(1,573,811	)		26,618
Depreciation expenses		—		(384,832	)		(2,489,070	)		(625,712	)		(196,201	)		—			(3,695,815	)
Impairment losses		—		—			(9,938	)		—			—			—			(9,938	)
Exchange adjustment		—		—			(4	)		—			(5	)		—			(9	)

December 31		452,738		4,095,929			11,163,121			896,476			434,791			936,389			17,979,444

December 31
Cost		452,738		10,821,972			51,244,512			5,008,321			1,937,755			936,389			70,401,687
Accumulated depreciation and impairment		—		(6,726,043	)		(40,081,391	)		(4,111,845	)		(1,502,964	)		—			(52,422,243	)

		452,738		4,095,929			11,163,121			896,476			434,791			936,389			17,979,444


	2020
	Land		Buildings			Machinery and equipment			Tools			Others			Construction in progress and equipment to be inspected			Total
	NT$000		NT$000			NT$000			NT$000			NT$000			NT$000			NT$000
January 1
Cost		452,738		10,821,972			51,244,512			5,008,321			1,937,755			936,389			70,401,687
Accumulated depreciation and impairment		—		(6,726,043	)		(40,081,391	)		(4,111,845	)		(1,502,964	)		—			(52,422,243	)

		452,738		4,095,929			11,163,121			896,476			434,791			936,389			17,979,444

January 1		452,738		4,095,929			11,163,121			896,476			434,791			936,389			17,979,444
Additions		—		132,572			592,565			409,832			142,776			2,855,870			4,133,615
Disposals		—		—			(8,940	)		(3,121	)		(7,297	)		—			(19,358	)
Reclassifications		—		258,421			2,336,238			398,798			159,195			(3,152,652	)		—
Depreciation expenses		—		(394,636	)		(2,734,667	)		(749,624	)		(220,066	)		—			(4,098,993	)
Exchange adjustment		—		—			(20	)		—			(2	)		—			(22	)

December 31		452,738		4,092,286			11,348,297			952,361			509,397			639,607			17,994,686

December 31
Cost		452,738		11,212,129			53,246,474			5,451,547			2,185,299			639,607			73,187,794
Accumulated depreciation and impairment		—		(7,119,843	)		(41,898,177	)		(4,499,186	)		(1,675,902	)		—			(55,193,108	)

		452,738		4,092,286			11,348,297			952,361			509,397			639,607			17,994,686

Capitalization Interest and Capitalization Interest Rate Applied Related to Property, Plant and Equipment


	Year ended December 31,
	2018			2019			2020
	NT$000			NT$000			NT$000
Amount of interest capitalized		18,542			15,114			9,762
Range of the interest rates for capitalization		1.7582	%		1.7822	%		1.4909	%

Leasing arrangements - leasee (Tables)

12 Months Ended

Dec. 31, 2020

Presentation of leases for lessee [abstract]

Summary of carrying amount of right-of-use assets and the depreciation expenses


	December 31, 2019		December 31, 2020
	Carrying amount		Carrying amount
	NT$000		NT$000
Land		669,967		636,261
Buildings		15,043		19,044
Machinery and equipment		—		203,249
Others		2,058		515

		687,068		859,069


	Year ended December 31,
	2019		2020
	Depreciation expenses		Depreciation expenses
	NT$000		NT$000
Land		22,657		20,938
Buildings		7,113		7,819
Machinery and equipment		4,520		46,225
Others		1,809		1,544

		36,099		76,526

Summary of profit and loss accounts relating to lease contracts


	Year ended December 31,
	2019		2020
	NT$000		NT$000
Items affecting profit or loss
Interest expense on lease liabilities		14,349		13,442
Expense on short-term lease contracts		230,589		202,782

Accounts payable (Tables)

12 Months Ended

Dec. 31, 2020

Disclosure Of Detailed Information Of Trade And Other Payable Explanatory [Abstract]

Summary of Accounts Payable


	December 31, 2019		December 31, 2020
	NT$000		NT$000
Accounts payable		419,520		766,805
Estimated accounts payable		400,028		200,016

		819,548		966,821

Other Payables (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Other Payables


	December 31, 2019		December 31, 2020
	NT$000		NT$000
Payables to contractors and equipment suppliers		972,770		1,145,359
Employees’ compensation payable		338,356		332,080
Salaries and bonuses payable		741,027		788,720
Pension payable		31,009		15,159
Directors’ remuneration payable		16,918		16,604
Interest payable		889		1,958
Other expense payable		876,067		949,523

		2,977,036		3,249,403

Long-term bank loans (Tables)

12 Months Ended

Dec. 31, 2020

Statement [LineItems]

Summary of Bank Loans


Type of loans	Period and payment term	December 31, 2019			December 31, 2020
		NT$000			NT$000
Syndicated bank loan	Borrowing period is from May 30, 2018 to May 30, 2023; interest is repayable monthly; principal is repayable semi-annually from November 30, 2018		9,066,000			3,310,000
Government granted bank loans	Borrowing period is from March 11, 2020 to February 15, 2030; interest is repayable monthly; principal is repayable monthly from March 15, 2023		—			4,505,000
Less: Fee on syndicated bank loan			(24,355	)		(17,223	)
Less: Unamortized interest on government granted bank loans			—			(64,212	)
Less: Current portion (fee included)			(748,419	)		(748,353	)

			8,293,226			6,985,212

Interest rate range			1.7895	%		0.65%~1.7895	%

Unused credit lines of long-term NT$000			1,800,000			11,239,000

Pensions (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Amounts Recognized in Statements of Financial Position

(a)

The amounts recognized in the statements of financial position are as follows:


	December 31, 2019			December 31, 2020
	NT$000			NT$000
Present value of defined benefit obligations		(901,159	)		(943,391	)
Fair value of plan assets		421,052			431,740

Net defined benefit liability		(480,107	)		(511,651	)

Summary of Movements in net Defined Benefit Liability

(b)

Movements in net defined benefit liability are as follows:


	2018
	Present value of defined benefit obligations			Fair value of plan assets			Net defined benefit liability
	NT$000			NT$000			NT$000
January 1		(838,543	)		360,017			(478,526	)
Current services cost		(382	)		—			(382	)
Interest (expense) income		(14,429	)		6,291			(8,138	)

		(853,354	)		366,308			(487,046	)

Remeasurements:
Return on plan assets (excluding amounts included in interest income or expense)		—			8,145			8,145
Financial assumption movement effect		(56,934	)		—			(56,934	)
Experience adjustments		(11,172	)		—			(11,172	)

		(68,106	)		8,145			(59,961	)

Pension fund contribution		—			26,242			26,242
Paid pension		11,379			(11,379	)		—

December 31		(910,081	)		389,316			(520,765	)


	2019
	Present value of defined benefit obligations			Fair value of plan assets			Net defined benefit liability
	NT$000			NT$000			NT$000
January 1		(910,081	)		389,316			(520,765	)
Current services cost		(332	)		—			(332	)
Interest (expense) income		(11,170	)		4,831			(6,339	)

		(921,583	)		394,147			(527,436	)

Remeasurements:
Return on plan assets (excluding amounts included in interest income or expense)		—			12,601			12,601
Financial assumption movement effect		(27,993	)		—			(27,993	)
Experience adjustments		36,308			—			36,308

		8,315			12,601			20,916

Pension fund contribution		—			26,413			26,413
Paid pension		12,109			(12,109	)		—

December 31		(901,159	)		421,052			(480,107	)


	2020
	Present value of defined benefit obligations			Fair value of plan assets			Net defined benefit liability
	NT$000			NT$000			NT$000
January 1		(901,159	)		421,052			(480,107	)
Current services cost		(263	)		—			(263	)
Interest (expense) income		(8,835	)		4,171			(4,664	)

		(910,257	)		425,223			(485,034	)

Remeasurements:
Return on plan assets (excluding amounts included in interest income or expense)		—			12,568			12,568
Financial assumption movement effect		(57,180	)		—			(57,180	)
Experience adjustments		(7,378	)		—			(7,378	)

		(64,558	)		12,568			(51,990	)

Pension fund contribution		—			25,373			25,373
Paid pension		31,424			(31,424	)		—

December 31		(943,391	)		431,740			(511,651	)

Principal Actuarial Assumptions

(d)

The principal actuarial assumptions used were as follows:


	Year ended December 31,
	2019			2020
Discount rate		1.00	%		0.50	%

Future salary increase		3.50	%		3.50	%

Sensitivity Analysis of Present Value of Defined Benefit Obligations Effected by Changes of Significant Actuarial Assumptions

Because the main actuarial assumption changed, the present value of defined benefit obligations is affected. The analysis was as follows:


	Discount rate					Future salary increase
	Increase 0.25%			Decrease 0.25%		Increase 0.25%		Decrease 0.25%
	NT$000			NT$000		NT$000		NT$000
December 31, 2019
Effect on present value of defined benefit obligations		(27,993	)		29,284		28,501		(27,407	)

December 31, 2020
Effect on present value of defined benefit obligations		(29,114	)		30,434		29,471		(28,365	)

Analysis of Timing of the Future Pension Payment

(f)

As of December 31, 2020, the weighted average duration of that retirement plan is 12.6 years. The analysis of timing of the future pension payment was as follows:


	December 31, 2020
	NT$000
Within 1 year		35,066
1-2 years		35,198
2-5 years		122,969
5-10 years		165,979

		359,212

Share-based payments (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Issuance of Restricted Shares

Type of

arrangement

Grant
date

Share price
on grant date
(in NT$)

Number of
shares
(in thousands)

Contract
period

Vesting condition

Restricted shares award agreement

July 21,
2015

36.1

15,752

3 years

Meet service and performance conditions

Restricted shares award agreement

May 10,
2016

30.6

1,548

3 years

Meet service and performance conditions

Capital stock (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Movement of Ordinary Shares Issued

Movements in the number of the Company’s ordinary shares outstanding are as follows:


	2018			2019			2020
	in thousands			in thousands			in thousands
January 1		856,059			727,265			727,240
Restricted shares – cancelled		(349	)		(25	)		—
Restricted shares – uncancelled		(23	)		—			—
Capital reduction		(128,422	)		—			—

December 31		727,265			727,240			727,240

Movement of Treasury Stock


	2018
	Shares			Amount
	in thousands			NT$000
January 1		30,085			1,007,654
Capital reduction		(4,515	)		(45,151	)

December 31		25,570			962,503

Capital surplus (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Capital Surplus


	2018
	Share premium		Employee restricted shares			Others		Total
	NT$000		NT$000			NT$000		NT$000
January 1		5,873,743		390,401			7,304		6,271,448
Share-based payments		—		(7,967	)		—		(7,967	)
Capital reduction		—		72			—		72

December 31		5,873,743		382,506			7,304		6,263,553


	2019
	Share premium			Employee restricted shares			Others		Total
	NT$000			NT$000			NT$000		NT$000
January 1		5,873,743			382,506			7,304		6,263,553
Share-based payments		—			(412	)		—		(412	)
Cancellation of treasury stock		(199,501	)		(12,853	)		—		(212,354	)

December 31		5,674,242			369,241			7,304		6,050,787


	2020
	Share premium		Employee restricted shares			Others		Total
	NT$000		NT$000			NT$000		NT$000
January 1		5,674,242		369,241			7,304		6,050,787
Reclassifications		369,241		(369,241	)		—		—

December 31		6,043,483		—			7,304		6,050,787

Retained earnings (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Distribution Towards Legal Reserve and Cash Dividend


	2017				2018				2019
	Amount		Cash Distribution per share		Amount		Cash Distribution per share		Amount		Cash Distribution per share
	Amount		Cash Distribution per share		Amount		Cash Distribution per share		Amount		Cash Distribution per share
	NT$000		NT$		NT$000		NT$		NT$000		NT$
Legal reserve		302,653				110,308				258,416
Special reserve		—				—				19,802
Cash dividend		256,806		0.30		872,718		1.20		1,309,032		1.80

Other equity interest (Tables)

12 Months Ended

Dec. 31, 2020

Other reserves [abstract]

Summary of Other Equity Interest


	2018
	Financial statements translation differences of foreign operations			Unrealized gain (loss) on valuation of financial assets at fair value through other comprehensive income			Unrealized gain on valuation of available-for-sale financial assets			Unearned employee awards			Total
	NT$000			NT$000			NT$000			NT$000			NT$000
January 1		65,593			—			678			(54,570	)		11,701
Effects on initial application of IFRS 9		—			42,843			(678	)		—			42,165

Adjusted beginning balance		65,593			42,843			—			(54,570	)		53,866
Currency translation differences
- The Company		(51,077	)		—			—			—			(51,077	)
Employee restricted shares
- The Company		—			—			—			52,869			52,869
Evaluation adjustment
- The Company		—			85,022			—			—			85,022
- Associates		—			(2,438	)		—			—			(2,438	)
Evaluation adjustment related tax
- The Company		—			(18,529	)		—			—			(18,529	)

December 31		14,516			106,898			—			(1,701	)		119,713


	2019
	Financial statements translation differences of foreign operations			Unrealized gain (loss) on valuation of financial assets at fair value through other comprehensive income			Unearned employee awards			Total
	NT$000			NT$000			NT$000			NT$000
January 1		14,516			106,898			(1,701	)		119,713
Currency translation differences
- The Company		(104,198	)		—			—			(104,198	)
Employee restricted shares
- The Company		—			—			1,701			1,701
Evaluation adjustment
- The Company		—			(52,549	)		—			(52,549	)
- Associates		—			5,093			—			5,093
Evaluation adjustment related tax
- The Company		—			7,016			—			7,016
Disposal of investment accounted for using equity method		—			(72	)		—			(72	)

December 31		(89,682	)		66,386			—			(23,296	)


	2020
	Financial statements translation differences of foreign operations			Unrealized gain (loss) on valuation of financial assets at fair value through other comprehensive income			Total
	NT$000			NT$000			NT$000
January 1		(89,682	)		66,386			(23,296	)
Currency translation differences
- The Company		28,352			—			28,352
Evaluation adjustment
- The Company		—			140,199			140,199
- Associates		—			22,925			22,925
Evaluation adjustment related tax
- The Company		—			(34,794	)		(34,794	)

December 31		(61,330	)		194,716			133,386

Revenue (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Revenue from Contracts with Customers


	Year ended December 31,
	2018		2019		2020
	NT$000		NT$000		NT$000
Revenue from contracts with customers		18,480,027		20,337,881		23,011,381

Summary of Contract Assets and Liabilities

The Group has recognized the following contract assets and liabilities in relation to revenue from contracts with customers:


	January 1, 2019		December 31, 2019		December 31, 2020
	NT$000		NT$000		NT$000
Contract assets		299,835		377,869		389,016

Contract liabilities (Advance payments)		1,432		1,231		—

Other income (expenses), net (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Other Income (Expenses), Net


	Year ended December 31,
	2018			2019			2020
	NT$000			NT$000			NT$000
Gain on disposal of scrapped materials		59,380			43,652			51,077
Royalty income		43,224			12,336			2,962
Gain on disposal of items purchased on behalf of others		31,268			15,080			30,140
Gain on disposal of property, plant and equipment, net		14,274			20,271			48,070
Insurance compensation income		147			10,435			—
Impairment loss on property, plant and equipment		—			(9,938	)		—
Others		(779	)		1,092			3,329

		147,514			92,928			135,578

Interest income (Tables)

12 Months Ended

Dec. 31, 2020

Disclosure of Interest Income [Abstract]

Disclosure of Interest Income


	Year ended December 31,
	2018		2019		2020
	NT$000		NT$000		NT$000
Bank deposits		49,051		59,901		25,547
Imputed interest from deposits		—		—		25
Financial assets at amortized cost		920		4,467		2,206

		49,971		64,368		27,778

Other income (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Other income


	Year ended December 31,
	2018		2019		2020
	NT$000		NT$000		NT$000
Rental income		7,819		9,249		10,260
Dividend income		571		585		3,229
Grant income		—		925		7,668

		8,390		10,759		21,157

Other gains and losses (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Other gains and losses


	Year ended December 31,
	2018		2019			2020
	NT$000		NT$000			NT$000
Foreign exchange gains (losses), net		93,104		(154,993	)		(355,255	)
Reimbursement of ADSs service charge		13,269		4,292			2,101
Gain on valuation of financial assets at fair value through profit or loss		1,485		1,317			24,015
Others		6,851		970			5,872

		114,709		(148,414	)		(323,267	)

Finance costs (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Finance Costs


	Year ended December 31,
	2018			2019			2020
	NT$000			NT$000			NT$000
Interest expense
Bank loans		170,476			171,840			158,720
Lease liabilities		—			14,349			13,442
Lease obligations payable		482			—			—
Less: Amounts capitalized in qualifying assets		(18,542	)		(15,114	)		(9,762	)

		152,416			171,075			162,400
Finance expense		37,832			9,187			9,082

		190,248			180,262			171,482

Expenses by nature (Tables)

12 Months Ended

Dec. 31, 2020

Analysis of income and expense [abstract]

Summary of Expenses by nature


	Year ended December 31,
	2018		2019		2020
	NT$000		NT$000		NT$000
Raw materials and supplies used		3,079,909		3,575,283		4,708,493
Employee benefit expenses		5,606,833		6,075,773		6,010,227
Depreciation expenses		3,376,579		3,731,914		4,175,519
Others		4,464,499		4,590,720		4,686,218

		16,527,820		17,973,690		19,580,457

Employee benefit expenses (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Employee benefit expenses


	Year ended December 31,
	2018		2019		2020
	NT$000		NT$000		NT$000
Salaries		4,628,039		5,114,790		4,937,591
Directors’ remuneration		18,456		26,266		28,229
Labor and health insurance		406,111		422,106		396,796
Pension		201,567		194,173		189,489
Share-based payments		41,043		822		—
Other personnel expenses		311,617		317,616		458,122

		5,606,833		6,075,773		6,010,227

For the year of 2019, employees’ compensation and directors’ remuneration recognized were consistent with the amounts resolved in the Board of Directors’ meetings.

Income tax expense (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Major Components of Income Tax Expense

(a)

Components of income tax expense:


	Year ended December 31,
	2018			2019			2020
	NT$000			NT$000			NT$000
Current income tax:
Current income tax on profits for the period		326,057			408,788			636,876
Income tax on unappropriated retained earnings		28,165			74,540			105,665
Prior year income tax under (over) estimation		3,729			(5,016	)		(133,923	)

Total current income tax		357,951			478,312			608,618

Deferred income tax:
Relating to origination and reversal of temporary differences		101,441			35,367			(14,237	)
Impact of change in tax rate		(2,774	)		—			—

Total deferred income tax		98,667			35,367			(14,237	)

Income tax expense		456,618			513,679			594,381

Deferred Tax Charged to Other Comprehensive Income

(b)

The income tax (charge)/credit relating to components of other comprehensive income are as follows:


	Year ended December 31,
	2018			2019			2020
	NT$000			NT$000			NT$000
Unrealized gain (loss) on valuation of financial assets at fair value through other comprehensive income		17,005			(7,016	)		34,794
Remeasurement of defined benefit obligations		(11,992	)		4,183			(10,398	)
Impact of change in tax rate		(887	)		—			—

		4,126			(2,833	)		24,396

Reconciliation of Income Tax Expense and Accounting Profit Before Income Tax

Reconciliation of income tax expense and the accounting profit:


	Year ended December 31,
	2018			2019			2020
	NT$000			NT$000			NT$000
Tax calculated based on profit before tax and statutory tax rate		356,488			606,917			595,258
Effects from adjustments based on regulation		81,042			(162,924	)		26,974
Temporary difference not recognized as deferred tax assets		(10,951	)		(608	)		(4	)
Prior year income tax under (over) estimation		3,729			(5,016	)		(133,923	)
Income tax on unappropriated retained earnings		28,165			74,540			105,665
Impact of change in tax rate		(2,774	)		—			—
Effect of different tax rates in countries in which the Group operates		919			770			411

Income tax expense		456,618			513,679			594,381

Details of Deferred Tax Assets (Liabilities)

The amounts of deferred tax assets or liabilities resulting from temporary differences and investment tax credits are as follows:


	2018
	January 1			Effects on initial application of IFRS 9 and IFRS 15			Recognized in profit or loss			Recognized in other comprehensive income			December 31
	NT$000			NT$000			NT$000			NT$000			NT$000
Deferred tax assets
Loss on inventories		9,132			(770	)		(1,130	)		—			7,232
Property, plant and equipment		55,494			—			8,689			—			64,183
Provisions		21,643			—			(9,247	)		—			12,396
Deferred revenue		39,485			—			(5,329	)		—			34,156
Net defined benefit liability		78,451			—			7,889			14,403			100,743
Unrealized exchange losses		8,167			144			(4,736	)		—			3,575
Investment tax credit		—			—			4,420			—			4,420
Others		—			—			11			—			11

Total		212,372			(626	)		567			14,403			226,716

Deferred tax liabilities
Property, plant and equipment		(174,293	)		—			(107,301	)		—			(281,594	)
Contract assets		—			(8,067	)		8,067			—			—
Financial assets at fair value through other comprehensive income		—			(8,636	)		—			(18,529	)		(27,165	)

Total		(174,293	)		(16,703	)		(99,234	)		(18,529	)		(308,759	)

Information presented on statements of financial position:
Deferred tax assets		212,372												226,716

Deferred tax liabilities		(174,293	)											(308,759	)


	2019
	January 1			Recognized in profit or loss			Recognized in other comprehensive income			December 31
	NT$000			NT$000			NT$000			NT$000
Deferred tax assets
Loss on inventories		7,232			5,468			—			12,700
Property, plant and equipment		64,183			(25,515	)		—			38,668
Provisions		12,396			(6,796	)		—			5,600
Deferred revenue		34,156			(6,506	)		—			27,650
Net defined benefit liability		100,743			(3,948	)		(4,183	)		92,612
Unrealized exchange losses		3,575			13,721			—			17,296
Investment tax credit		4,420			(4,420	)		—			—
Others		11			15			—			26

Total		226,716			(27,981	)		(4,183	)		194,552

Deferred tax liabilities
Property, plant and equipment		(281,594	)		(7,386	)		—			(288,980	)
Financial assets at fair value through other comprehensive income		(27,165	)		—			7,016			(20,149	)

Total		(308,759	)		(7,386	)		7,016			(309,129	)

Information presented on statements of financial position
Deferred tax assets		226,716									194,552

Deferred tax liabilities		(308,759	)								(309,129	)


	2020
	January 1			Recognized in profit or loss			Recognized in other comprehensive income			December 31
	NT$000			NT$000			NT$000			NT$000
Deferred tax assets
Loss on inventories		12,700			3,263			—			15,963
Property, plant and equipment		38,668			(2,267	)		—			36,401
Provisions		5,600			(2,922	)		—			2,678
Deferred revenue		27,650			(6,506	)		—			21,144
Net defined benefit liability		92,612			(4,089	)		10,398			98,921
Unrealized exchange losses		17,296			(7,381	)		—			9,915
Others		26			643			—			669

Total		194,552			(19,259	)		10,398			185,691

Deferred tax liabilities
Property, plant and equipment		(288,980	)		33,496			—			(255,484	)
Financial assets at fair value through other comprehensive income		(20,149	)		—			(34,794	)		(54,943	)

Total		(309,129	)		33,496			(34,794	)		(310,427	)

Information presented on statements of financial position
Deferred tax assets		194,552									185,691

Deferred tax liabilities		(309,129	)								(310,427	)

Earnings per share (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Income and Share Data Used in Basic and Diluted EPS Computations

Year ended December 31, 2018

Amount

after income
tax

Weighted average
number of ordinary
shares outstanding

Earnings

per share

Basic earnings per share

NT$000

In thousands

NT$

Profit attributable to equity holders of the Company

1,325,824

802,725

1.65

Diluted earnings per share

Assumed conversion of all dilutive potential ordinary shares:

Employees’ compensation

7,626

Restricted shares

3,356

Profit attributable to equity holders of the Company

1,325,824

813,707

1.63

Year ended December 31, 2019

Amount

after income
tax

Weighted average

number of ordinary
shares outstanding

Earnings

per share

Basic earnings per share

NT$000

In thousands

NT$

Profit attributable to equity holders of the Company

2,508,574

727,111

3.45

Diluted earnings per share

Assumed conversion of all dilutive potential ordinary shares:

Employees’ compensation

9,879

Restricted shares

126

Profit attributable to equity holders of the Company

2,508,574

737,116

3.40

Year ended December 31, 2020

Amount

after income
tax

Weighted average
number of ordinary
shares outstanding

Earnings

per share

Basic earnings per share

NT$000

In thousands

NT$

Profit attributable to equity holders of the Company

2,378,978

727,240

3.27

Diluted earnings per share

Assumed conversion of all dilutive potential ordinary shares:

Employees’ compensation

9,668

Profit attributable to equity holders of the Company

2,378,978

736,908

3.23

Supplementary cash flow information (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Partial Cash Paid for Investing Activities

Property, plant and equipment


	Year ended December 31,
	2018			2019			2020
	NT$000			NT$000			NT$000
Purchase of property, plant and equipment		4,945,570			4,896,656			4,133,615
Add: Beginning balance of payable to contractors and equipment suppliers		713,313			1,516,735			972,770
Add: Beginning balance of payable on lease		29,842			—			—
Less: Ending balance of payable to contractors and equipment suppliers		(1,516,735	)		(972,770	)		(1,145,359	)
Less: Ending balance of payable on lease		(17,792	)		—			—

Cash paid during the year		4,154,198			5,440,621			3,961,026

Changes in liabilities from financing activities (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Reconciliation of Liabilities Arising from Financing Activities


	2018
	Short-term bank loans			Long-term bank loans (including current portion)		Guarantee deposits			Total liabilities from financing activities
	NT$000			NT$000		NT$000			NT$000
January 1		969,353			9,642,021		1,371			10,612,745
Changes in cash flow from financing activities		(969,353	)		110,250		(279	)		(859,382	)
Amortization of loan fees		—			37,247		—			37,247

December 31		—			9,789,518		1,092			9,790,610


	2019
	Long-term bank loans (including current portion)			Guarantee deposits		Lease liabilities			Total liabilities from financing activities
	NT$000			NT$000		NT$000			NT$000
January 1		9,789,518			1,092		—			9,790,610
Effects on initial application of IFRS 16		—			—		884,275			884,275

Adjusted balance at January 1		9,789,518			1,092		884,275			10,674,885
Changes in cash flow from financing activities		(756,450	)		3		(48,161	)		(804,608	)
Adjustment to right-of-use assets		—			—		(148,512	)		(148,512	)
Reclassification to payable on equipment from lease liabilities		—			—		(9,000	)		(9,000	)
Amortization of loan fees		8,577			—		—			8,577
Amortization of interest expense		—			—		14,349			14,349

December 31		9,041,645			1,095		692,951			9,735,691


	2020
	Long-term bank loans (including current portion)			Guarantee deposits		Lease liabilities			Total liabilities from financing activities
	NT$000			NT$000		NT$000			NT$000
January 1		9,041,645			1,095		692,951			9,735,691
Changes in cash flow from financing activities		(1,326,857	)		575		(84,928	)		(1,411,210	)
Adjustment to right-of-use assets		—			—		249,030			249,030
Reclassification		—			20,000		—			20,000
Amortization of loan fees		7,581			—		—			7,581
Amortization of interest expense		11,196			—		13,442			24,638

December 31		7,733,565			21,670		870,495			8,625,730

Related party transactions (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Significant Related Party Transactions


	b)	Names of related parties and relationship


Name	Relationship
Unimos Shanghai		Associate
JMC		Associate

Significant related party transactions

(a)

Purchases of materials


	Year ended December 31,
	2018		2019		2020
	NT$000		NT$000		NT$000
JMC		132,494		9		—

Key Management Personnel Compensation


	d)	Key management personnel compensation


	Year ended December 31,
	2018		2019		2020
	NT$000		NT$000		NT$000
Salaries and other short-term employee benefits		151,095		178,713		186,854
Post-employment compensation		2,067		2,049		4,258
Share-based payments		6,763		—		—

		159,925		180,762		191,112

Pledged assets (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Certain Assets Provided as Collateral Mainly for Long-term Bank Loans and Leases

Assets

Purpose

December 31,
2019

December 31,
2020

Carry
amount

NT$000

Non-current

financial assets at amortized cost

Lease and
bank loan

68,450

48,319

Property, plant and equipment, net

- Land

Bank loan

452,738

- Buildings

Bank loan

4,095,929

4,092,287

- Machinery and equipment

Bank loan

4,105,912

6,912,544

8,723,029

11,505,888

Significant contingent liabilities and unrecognized contract commitments (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Capital Expenditures that are Contracted for, but not Provided for

Capital expenditures that are contracted for, but not provided for are as follows:


	December 31, 2019		December 31, 2020
	NT$000		NT$000
Property, plant and equipment, net		1,640,712		2,331,041

Capital management (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Group Monitors Capital using Liabilities to Assets Ratio

The liabilities to assets ratio at December 31, 2019 and 2020 were as follows:


	December 31, 2019			December 31, 2020
	NT$000			NT$000
Total liabilities		14,775,302			14,364,975
Total assets		34,305,887			35,080,814

Liabilities to assets ratio		43.07	%		40.95	%

Financial risk management and fair values of financial instruments (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Financial Instruments by Category


	a)	Financial instruments

(a)

Financial instruments by category


	December 31, 2019		December 31, 2020
	NT$000		NT$000
Financial assets
Financial assets at fair value through profit or loss
Financial assets mandatorily measured at fair value through profit or loss		11,038		63,488
Financial assets at fair value through other comprehensive income
Designation of equity instruments		121,808		262,007
Financial assets at amortized cost
Cash and cash equivalents		4,704,084		4,113,651
Financial assets at amortized cost		237,420		254,801
Notes receivable		765		599
Accounts receivable		4,452,904		5,364,156
Accounts receivable – related parties		1,045		—
Other receivables		89,676		51,436
Other receivables – related parties		2,948		—
Refundable deposits		21,145		21,186

		9,642,833		10,131,324

Financial liabilities
Financial liabilities at amortized cost
Notes payable		—		2,899
Accounts payable		819,548		966,821
Other payables		2,977,036		3,249,403
Long-term bank loans (including current portion)		9,041,645		7,733,565
Guarantee deposits		1,095		21,670

		12,839,324		11,974,358

Lease liabilities (including current portion)		692,951		870,495

Information on Assets and Liabilities Denominated in Foreign Currencies whose Values would be Materially Affected by Exchange Rate Fluctuations

The information on assets and liabilities denominated in foreign currencies whose values would be materially affected by the exchange rate fluctuations is as follows:


	December 31, 2019
	Foreign currency		Exchange rate		Carrying amount (NT$000)
(Foreign currency: functional currency)
Financial assets
Monetary items
US$000		188,369		29.9800		5,647,303
JPY000		266,819		0.2760		73,642
RMB000		6,197		4.3050		26,678
Non-monetary items
JPY000		441,334		0.2760		121,808
RMB000		730,108		4.3050		3,143,117
Financial liabilities
Monetary items
US$000		7,867		29.9800		235,853
JPY000		1,033,394		0.2760		285,217


	December 31, 2020
	Foreign currency		Exchange rate		Carrying amount (NT$000)
(Foreign currency: functional currency)
Financial assets
Monetary items
US$000		175,840		28.4800		5,007,923
JPY000		137,635		0.2763		38,029
RMB000		6,838		4.3770		29,930
Non-monetary items
JPY000		948,270		0.2763		262,007
RMB000		690,178		4.3770		3,020,908
Financial liabilities
Monetary items
US$000		26,410		28.4800		752,157
JPY000		1,538,241		0.2763		425,016

Details of Exposure to Currency Risk Arising from Recognized Monetary Assets or Liabilities Denominated in a Currency Other Than Functional Currency

Analysis of foreign currency market risk arising from significant foreign exchange variations:


	Year ended December 31, 2018
	Sensitivity analysis
	Change in exchange rate			Effect on profit (loss) (NT$000)		Effect on other comprehensive income (NT$000)
Financial assets
Monetary items
US$000		5	%		261,492		—
JPY000		5	%		2,470		—
RMB000		5	%		1,979		—
Financial liabilities
Monetary items
US$000		5	%		27,997		—
JPY000		5	%		33,887		—


	Year ended December 31, 2019
	Sensitivity analysis
	Change in exchange rate			Effect on profit (loss) (NT$000)		Effect on other comprehensive income (NT$000)
Financial assets
Monetary items
US$000		5	%		282,365		—
JPY000		5	%		3,682		—
RMB000		5	%		1,334		—
Financial liabilities
Monetary items
US$000		5	%		11,793		—
JPY000		5	%		14,261		—


	Year ended December 31, 2020
	Sensitivity analysis
	Change in exchange rate			Effect on profit (loss) (NT$000)		Effect on other comprehensive income (NT$000)
Financial assets
Monetary items
US$000		5	%		250,396		—
JPY000		5	%		1,901		—
RMB000		5	%		1,497		—
Financial liabilities
Monetary items
US$000		5	%		37,608		—
JPY000		5	%		21,251		—

Summary of Loss Rate Methodology

As of December 31, 2019 and 2020 the loss rate methodologies are as follows:


	December 31, 2019
	Contract assets			Accounts receivable (including related parties)			Other receivables (including related parties)
	NT$000			NT$000			NT$000
Expected loss rate		0.030	%		0.030	%		0.030	%
Total carrying amount		377,983			4,455,300			92,642
Loss allowance		(114	)		(1,351	)		(18	)


	December 31, 2020
	Contract assets			Accounts receivable (including related parties)			Other receivables (including related parties)
	NT$000			NT$000			NT$000
Expected loss rate		0.030	%		0.030	%		0.030	%
Total carrying amount		389,133			5,365,776			51,446
Loss allowance		(117	)		(1,620	)		(10	)

Summary of Movements in Relation to Loss Allowance for Contract Assets, Accounts Receivable and Other Receivables

Under the simplified approach, movements in relation to loss allowance for contract assets, accounts receivable, and other receivables are as follows:


	2018
	Contract assets			Accounts receivable (including related parties)			Other receivables (including related parties)
	NT$000			NT$000			NT$000
January 1_ IAS 39		—			—			—
Adjustments for applying new standards		(115	)		(1,819	)		(7	)

January 1_IFRS 9		(115	)		(1,819	)		(7	)
Provision for impairment loss		(20	)		(322	)		(7	)
Reversal of impairment loss		—			—			1

December 31		(135	)		(2,141	)		(13	)


	2019
	Contract assets			Accounts receivable (including related parties)			Other receivables (including related parties)
	NT$000			NT$000			NT$000
January 1		(135	)		(2,141	)		(13	)
Provision for impairment loss		—			—			(5	)
Reversal of impairment loss		21			790			—

December 31		(114	)		(1,351	)		(18	)


	2020
	Contract assets			Accounts receivable (including related parties)			Other receivables (including related parties)
	NT$000			NT$000			NT$000
January 1		(114	)		(1,351	)		(18	)
Provision for impairment loss		(3	)		(269	)		—
Reversal of impairment loss		—			—			8

December 31		(117	)		(1,620	)		(10	)

Maturity Profile of Non-derivative Financial Liabilities Based on Contracted Undiscounted Payments


	December 31, 2019
	Within 1 year		1 to 3 years		3 to 5 years		Over 5 years		Total
	NT$000		NT$000		NT$000		NT$000		NT$000
Non-derivative financial liabilities
Long-term bank loans		914,159		1,786,842		6,848,327		—		9,549,328
Lease liabilities		36,806		60,111		57,836		762,699		917,452
Guarantee deposits		—		—		—		1,095		1,095

		950,965		1,846,953		6,906,163		763,794		10,467,875


	December 31, 2020
	Within 1 year		1 to 3 years		3 to 5 years		Over 5 years		Total
	NT$000		NT$000		NT$000		NT$000		NT$000
Non-derivative financial liabilities
Long-term bank loans		846,401		3,558,597		2,198,717		1,487,808		8,091,523
Lease liabilities		145,594		160,146		54,689		718,752		1,079,181
Guarantee deposits		—		—		—		21,670		21,670

		991,995		3,718,743		2,253,406		2,228,230		9,192,374

Summary of Natures of Assets and Liabilities

The related information of natures of the assets and liabilities is as follows:


	December 31, 2019
	Level 1		Level 2		Level 3		Total
	NT$000		NT$000		NT$000		NT$000
Assets
Recurring fair value measurements
Financial assets at fair value through profit or loss
- Foreign partnership interests		—		—		11,038		11,038
Financial assets at fair value through other comprehensive income
- Foreign unlisted stocks		—		—		121,808		121,808

		—		—		132,846		132,846


	December 31, 2020
	Level 1		Level 2		Level 3		Total
	NT$000		NT$000		NT$000		NT$000
Assets
Recurring fair value measurements
Financial assets at fair value through profit or loss
- Listed stocks		53,120		—		—		53,120
- Foreign partnership interests		—		—		10,368		10,368
Financial assets at fair value through other comprehensive income
- Foreign unlisted stocks		—		—		262,007		262,007

		53,120		—		272,375		325,495

Summary of Movements of Level 3

(d)

The following table shows the movements of Level 3 for the years ended December 31, 2019 and 2020:


	December 31, 2019
	Debt instruments			Equity instruments			Total
	NT$000			NT$000			NT$000
January 1		11,471			174,357			185,828
Gains or losses recognized in profit or loss
Recorded as non-operating expenses		(433	)		—			(433	)
Gains or losses recognized in other comprehensive income
Recorded as unrealized losses on valuation of financial assets at fair value through other comprehensive income		—			(52,549	)		(52,549	)

December 31		11,038			121,808			132,846


	December 31, 2020
	Debt instruments			Equity instruments		Total
	NT$000			NT$000		NT$000
January 1		11,038			121,808		132,846
Gains or losses recognized in profit or loss
Recorded as non-operating expenses		(670	)		—		(670	)
Gains or losses recognized in other comprehensive income
Recorded as unrealized gains on valuation of financial assets at fair value through other comprehensive income		—			140,199		140,199

December 31		10,368			262,007		272,375

Summary of Qualitative Information and Sensitivity Analysis of Changes in Significant Unobservable Inputs Under Valuation Model Used in Level 3 Fair Value Measurement

(f)

The following is the qualitative information and sensitivity analysis of changes in significant unobservable inputs under valuation model used in Level 3 fair value measurement:

Fair value as of

December 31,
2019

Valuation

technique

Significant

unobservable
input

Range

(weighted

average
method)

Relationship of inputs

to fair value

NT$000

Non-derivative

debt instrument:

Foreign partnership interests

11,038

Discounted cash flow

Discount
rate

0.30

The lower the discount rate, the higher the fair value

Non-derivative

equity instrument:

Foreign unlisted stocks

121,808

Comparable

companies

Price to book
ratio
multiple

1.22

The higher the multiple, the higher the fair value

Enterprise
value to
EBITDA
multiple

10.51

The higher the multiple, the higher the fair value

Discount for
lack of
marketability

15.80

The higher the discount for lack of marketability, the lower the fair value

Fair value as of

December 31,
2020

Valuation

technique

Significant

unobservable
input

Range

(weighted

average
method)

Relationship of inputs

to fair value

NT$000

Non-derivative

debt instrument:

Foreign partnership interests

10,368

Discounted cash flow

Discount
rate

0.30

The lower the discount rate, the higher the fair value

Non-derivative

equity instrument:

Foreign unlisted stocks

262,007

Comparable

companies

Price to book
ratio
multiple

1.97

The higher the multiple, the higher the fair value

Enterprise
value to
EBITDA
multiple

12.00

The higher the multiple, the higher the fair value

Discount for
lack of
marketability

15.80

The higher the discount for lack of marketability, the lower the fair value

Summary of Effect of Profit or Loss or of Other Comprehensive Income from Financial Assets Categorized


			December 31, 2019
			Recognized in profit or loss				Recognized in other comprehensive income
	Input	Change	Favorable change		Unfavorable change		Favorable change		Unfavorable change
			NT$000		NT$000		NT$000		NT$000
Financial assets:
Foreign partnership interests	Discount rate	Note		—		—		—		—
Foreign unlisted stocks	Price to book ratio multiple	± 1%		—		—		53		53
	Enterprise value to EBITDA multiple	± 1%		—		—		850		900
	Discount for lack of marketability	± 1%		—		—		1,460		1,460

				—		—		2,363		2,413


						December 31, 2020
						Recognized in profit or loss				Recognized in other comprehensive income
	Input		Change			Favorable change		Unfavorable change		Favorable change		Unfavorable change
						NT$000		NT$000		NT$000		NT$000
Financial assets:
Foreign partnership interests		Discount rate		Note			—		—		—		—
Foreign unlisted stocks		Price to book ratio multiple		± 1	%		—		—		30		30
		Enterprise value to EBITDA multiple		± 1	%		—		—		2,153		2,153
		Discount for lack of marketability		± 1	%		—		—		3,142		3,084

							—		—		5,325		5,267

Segment Information (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Financial Segment Information for Operating Segments

The segment information provided to the chief operating decision maker for the reportable segments is as follows:


	Year ended December 31, 2018
	Testing			Assembly			LCDD			Bumping			Others			Elimination			Total
	NT$000			NT$000			NT$000			NT$000			NT$000			NT$000			NT$000
Revenue
External customers		4,790,097			4,679,676			5,694,720			3,315,534			—			—			18,480,027
Inter-segment		—			—			—			—			35,738			(35,738	)		—

Total revenue		4,790,097			4,679,676			5,694,720			3,315,534			35,738			(35,738	)		18,480,027

Operating profit (loss)		1,306,742			(207,700	)		1,226,755			(202,497	)		(23,433	)		(146	)		2,099,721

Depreciation expenses		(769,660	)		(578,205	)		(1,400,784	)		(627,412	)		(518	)		—			(3,376,579	)

Share of profit (loss) of associates		—			—			—			—			(668,377	)		368,276			(300,101	)

Interest income		—			—			—			—			49,971			—			49,971

Interest expense		—			—			—			—			(152,416	)		—			(152,416	)

Purchase of property, plant and equipment		1,563,919			321,976			2,732,141			327,251			283			—			4,945,570


	Year ended December 31, 2019
	Testing			Assembly			LCDD			Bumping			Others			Elimination			Total
	NT$000			NT$000			NT$000			NT$000			NT$000			NT$000			NT$000
Revenue
External customers		4,257,800			5,148,877			6,922,205			4,008,999			—			—			20,337,881
Inter-segment		—			—			—			—			32,808			(32,808	)		—

Total revenue		4,257,800			5,148,877			6,922,205			4,008,999			32,808			(32,808	)		20,337,881

Operating profit (loss)		709,142			(227,096	)		1,740,720			232,404			1,931			18			2,457,119

Depreciation expenses		(802,740	)		(521,311	)		(1,796,951	)		(604,553	)		(6,359	)		—			(3,731,914	)

Share of profit (loss) of associates		—			—			—			—			(370,351	)		215,425			(154,926	)

Interest income		—			—			—			—			64,368			—			64,368

Interest expense		—			—			—			—			(171,075	)		—			(171,075	)

Purchase of property, plant and equipment		764,105			548,063			3,077,806			506,635			47			—			4,896,656


	Year ended December 31, 2020
	Testing			Assembly			LCDD			Bumping			Others			Elimination			Total
	NT$000			NT$000			NT$000			NT$000			NT$000			NT$000			NT$000
Revenue
External customers		5,002,730			6,001,964			7,023,003			4,983,684			—			—			23,011,381
Inter-segment		—			—			—			—			39,646			(39,646	)		—

Total revenue		5,002,730			6,001,964			7,023,003			4,983,684			39,646			(39,646	)		23,011,381

Operating profit (loss)		1,333,682			67,730			1,687,986			487,323			(10,230	)		11			3,566,502

Depreciation expenses		(853,829	)		(523,341	)		(2,213,504	)		(578,890	)		(5,955	)		—			(4,175,519	)

Share of profit (loss) of associates		—			—			—			—			(320,578	)		173,249			(147,329	)

Interest income		—			—			—			—			27,778			—			27,778

Interest expense		—			—			—			—			(162,400	)		—			(162,400	)

Purchase of property, plant and equipment		887,204			803,693			2,143,401			298,834			483			—			4,133,615

Schedule of information on products and services

Information on products and services


	Year ended December 31,
	2018				2019				2020
	NT$000		%		NT$000		%		NT$000		%
Testing		4,790,097		26		4,257,800		21		5,002,730		22
Assembly		4,679,676		25		5,148,877		25		6,001,964		26
LCDD		5,694,720		31		6,922,205		34		7,023,003		30
Bumping		3,315,534		18		4,008,999		20		4,983,684		22

		18,480,027		100		20,337,881		100		23,011,381		100

Geographic Information of Revenue

Geographical information


	Year ended December 31,
	2018		2019		2020
	NT$000		NT$000		NT$000
Revenue
ROC		14,751,766		15,875,027		18,341,726
Japan		1,825,479		1,905,032		1,291,026
Singapore		1,143,661		1,333,114		1,838,394
PRC		163,831		789,496		1,105,535
Others		595,290		435,212		434,700

		18,480,027		20,337,881		23,011,381


	December 31, 2019		December 31, 2020
	NT$000		NT$000
Non-current assets
ROC		18,727,979		18,913,501
PRC		—		117
Others		5,659		11,845

		18,733,638		18,925,463

Net Revenue from Customers Representing at Least 10% of Total Revenue

The information on the major customers which constituted more than 10% of the Group’s total revenue for the years ended December 31, 2018, 2019 and 2020 is as follows:


	Year ended December 31,
	2018				2019				2020
	Amount		%		Amount		%		Amount		%
	NT$000				NT$000				NT$000
Customers
Customer A		3,794,991		21		4,756,755		23		5,088,544		22
Customer X		1,328,752		7		1,977,427		10		2,660,866		12
Customer K		2,637,053		14		2,419,612		12		2,332,914		10
Customer C		1,957,467		11		2,048,260		10		2,143,130		9

Financial Statements Schedule: Valuation and Qualifying Accounts (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Disclosure Of Details Of Valuation And Qualifying Accounts


	January 1		Additions charged to expense or deduction of revenue		Deduction / Write-offs / Reversal			December 31
	NT$000		NT$000		NT$000			NT$000
Year of 2018 :
Allowance for impairment of property, plant and equipment		320,455		—		(2,862	)		317,593
Allowance for impairment of obsolescence and decline in market value of inventories		53,714		—		(17,557	)		36,157
Provision for deficiency compensation		57,155		14,211		(42,014	)		29,352
Sales for allowance		70,156		44,950		(82,479	)		32,627
Year of 2019 :
Allowance for impairment of property, plant and equipment		317,593		9,938		(134,191	)		193,340
Allowance for impairment of obsolescence and decline in market value of inventories		36,157		27,341		—			63,498
Provision for deficiency compensation		29,352		5,204		(32,558	)		1,998
Sales for allowance		32,627		63,863		(70,490	)		26,000
Year of 2020 :
Allowance for impairment of property, plant and equipment		193,340		—		(11,338	)		182,002
Allowance for impairment of obsolescence and decline in market value of inventories		63,498		16,317		—			79,815
Provision for deficiency compensation		1,998		4,358		(2,893	)		3,463
Sales for allowance		26,000		21,916		(38,052	)		9,864

Effects on initial application of IFRS 16 (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Information About Differences Between Operating Lease Commitments And Lease Liabilities


	NT$000
Operating lease commitments disclosed by applying IAS 17 as of December 31, 2018		320,214
Add: Lease payable recognized under finance lease by applying IAS 17 as of December 31, 2018		17,792
Less: Short-term leases		(28,121	)
Add: Adjustments as a result of a different treatment of extension and termination options		874,298

Total lease contracts amount recognized as lease liabilities by applying IFRS 16 on January 1, 2019		1,184,183

Incremental borrowing interest rate at the date of initial application		1.7895%~3.9474	%

Lease liabilities recognized as of January 1, 2019 by applying IFRS 16		884,275

Effects on initial application of IFRS 9 (Tables)

12 Months Ended

Dec. 31, 2020

Text block [abstract]

Summary of Carrying Amount of Financial Assets Transferred

The carrying amount of financial assets transferred from December 31, 2017 under IAS 39 to January 1, 2018 under IFRS 9 is reconciled as follows:


																	Effects
	Note		Measured at cost			Measured at fair value through profit or loss		Measured at fair value through other comprehensive income		Other financial assets			Measured at amortized cost		Total		Retained earnings		Other equity interest
			NT$000			NT$000		NT$000		NT$000			NT$000		NT$000		NT$000		NT$000
IAS 39				20,890			—		—		70,241			—		91,131		—		—
Transferred into and measured at fair value through profit or loss		(c)		(10,940	)		10,940		—		—			—		—		—		—
Transferred into and measured at fair value through other comprehensive income		(b)		(9,950	)		—		9,950		—			—		—		—		—
Transfer into and measured at amortized cost		(a)		—			—		—		(70,241	)		70,241		—		—		—
Fair value adjustment		(b)(c)		—			493		50,801		—			—		51,294		493		79,385
Impairment loss adjustment		(b)		—			—		28,584		—			—		28,584		28,584		(28,584	)
Income tax adjustment		(b)		—			—		—		—			—		—		—		(8,636	)

IFRS 9				—			11,433		89,335		—			70,241		171,009		29,077		42,165

(a)

(b)

Given the Group’s

available-for-sale

(c)

The Group’s

available-for-sale

The authorization of the consolidated financial statements - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Date of authorization of financial statements by Board of directors	Apr. 20, 2021

Summary of Significant Accounting Policies - Summary of Ownership Interests in Subsidiaries (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
ChipMOS U.S.A., Inc. [member]
Disclosure of joint ventures [line items]
Name of investor	The Company
Main businesses	Marketing of semiconductors and electronic related products
Location	San Jose, USA
Percentage of Ownership (%)	100.00%	100.00%
ChipMOS TECHNOLOGIES (BVI) LTD. [member]
Disclosure of joint ventures [line items]
Name of investor	The Company
Main businesses	Holding company
Location	British Virgin Islands
Percentage of Ownership (%)	100.00%	100.00%
ChipMOS SEMICONDUCTORS (Shanghai) LTD. [Member]
Disclosure of joint ventures [line items]
Name of investor	ChipMOS BVI
Main businesses	Marketing of semiconductors and electronic related products
Location	Shanghai, People’s Republic of China (“PRC”)
Percentage of Ownership (%)	100.00%

Summary of Significant Accounting Policies - Estimated Useful Life for Depreciation of Individual Assets (Detail)	12 Months Ended
	Dec. 31, 2020
Buildings [member] \| Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Estimated useful life of individual assets	5 years
Buildings [member] \| Top of range [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Estimated useful life of individual assets	51 years
Machinery and equipment [member] \| Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Estimated useful life of individual assets	2 years
Machinery and equipment [member] \| Top of range [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Estimated useful life of individual assets	8 years
Tools [member] \| Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Estimated useful life of individual assets	2 years
Tools [member] \| Top of range [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Estimated useful life of individual assets	4 years
Other equipment [member] \| Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Estimated useful life of individual assets	2 years
Other equipment [member] \| Top of range [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Estimated useful life of individual assets	6 years

Translation into U.S. Dollar Amounts - Additional Information (Detail)	Dec. 31, 2020
Foreign exchange rates [abstract]
Foreign exchange rate from New Taiwan dollars to U.S. dollars at the noon buying rate in the City of New York for cable transfers as certified for customs purposes by the Federal Reserve Bank of New York	28.08

Cash and Cash Equivalents - Summary of Cash and Cash Equivalents (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)
Cash and cash equivalents [abstract]
Cash on hand and petty cash	$ 470		$ 470
Checking accounts and demand deposits	2,609,421		915,134
Time deposits	1,503,760		3,788,480
Cash and cash equivalents	$ 4,113,651	$ 146,498	$ 4,704,084

Financial Assets at Fair Value Through Profit or Loss - Summary of Financial Assets at Fair Value Through Profit or Loss (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)
Financial Assets At Fair Value Through Profit Or Loss [line items]
Current financial assets mandatorily measured at fair value through profit or loss	$ 53,120	$ 1,892
Non-current financial assets mandatorily measured at fair value through profit or loss	10,368		$ 11,038
Foreign partnership interest [member]
Financial Assets At Fair Value Through Profit Or Loss [line items]
Non-current financial assets mandatorily measured at fair value through profit or loss	10,940		10,940
Listed stocks [member]
Financial Assets At Fair Value Through Profit Or Loss [line items]
Current financial assets mandatorily measured at fair value through profit or loss	46,512
Valuation adjustments [member]
Financial Assets At Fair Value Through Profit Or Loss [line items]
Current financial assets mandatorily measured at fair value through profit or loss	6,608
Non-current financial assets mandatorily measured at fair value through profit or loss	$ (572)		$ 98

Financial Assets at Fair Value Through Profit or Loss - Summary of Amounts recognized in Profit or Loss in Relation to Financial Assets at Fair Value Through Profit or Loss (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Financial Assets At Fair Value Through Profit Or Loss [line items]
Financial assets mandatorily measured at fair value through profit or loss	$ 24,015	$ 855	$ 1,317	$ 1,485
Foreign partnership interest [member]
Financial Assets At Fair Value Through Profit Or Loss [line items]
Financial assets mandatorily measured at fair value through profit or loss	(670)		(433)	38
Beneficiary certificates [member]
Financial Assets At Fair Value Through Profit Or Loss [line items]
Financial assets mandatorily measured at fair value through profit or loss	18,077		$ 1,750	1,396
Derivative instrument [member]
Financial Assets At Fair Value Through Profit Or Loss [line items]
Financial assets mandatorily measured at fair value through profit or loss				$ 51
Listed stocks [member]
Financial Assets At Fair Value Through Profit Or Loss [line items]
Financial assets mandatorily measured at fair value through profit or loss	$ 6,608

Financial Assets at Amortized Cost - Summary of Financial Assets at Amortized Cost (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financial Instruments At Amortised Cost Category[abstract]
Time deposits	$ 206,482	$ 168,970
Restricted bank deposits	48,319	68,450
Interest income	$ 2,206	$ 4,467	$ 920

Accounts receivable - Summary of Accounts and notes receivable (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Jan. 01, 2019 TWD ($)
Disclosure of financial assets [Line Items]
Accounts receivable	$ 5,364,156	$ 191,031	$ 4,452,904
Accounts receivable [member]
Disclosure of financial assets [Line Items]
Accounts receivable	5,365,776		4,454,255	$ 4,745,693
Loss allowance [member]
Disclosure of financial assets [Line Items]
Accounts receivable	$ (1,620)		$ (1,351)

Accounts receivable - Additional Information (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Jan. 01, 2019 TWD ($)
Disclosure of financial assets [Line Items]
Accounts receivable from contract with customers	$ 5,364,156	$ 191,031	$ 4,452,904
Accounts receivable [member]
Disclosure of financial assets [Line Items]
Accounts receivable from contract with customers	$ 5,365,776		$ 4,454,255	$ 4,745,693
Bottom of range [member]
Disclosure of financial assets [Line Items]
Credit term granted to customers	30 days
Top of range [member]
Disclosure of financial assets [Line Items]
Credit term granted to customers	90 days

Accounts receivable - Aging of Accounts Receivable which are Past Due but not Impaired (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Jan. 01, 2019 TWD ($)
Disclosure of financial assets [Line Items]
Accounts receivable	$ 5,364,156	$ 191,031	$ 4,452,904
Accounts receivable [member]
Disclosure of financial assets [Line Items]
Accounts receivable	5,365,776		4,454,255	$ 4,745,693
Accounts receivable [member] \| Current [member]
Disclosure of financial assets [Line Items]
Accounts receivable	5,272,208		4,440,081
Accounts receivable [member] \| Within 1 month [member]
Disclosure of financial assets [Line Items]
Accounts receivable	$ 93,568		13,733
Accounts receivable [member] \| 1 - 2 months [member]
Disclosure of financial assets [Line Items]
Accounts receivable			$ 441

Inventories - Summary of Inventories (Detail) - TWD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Disclosure of inventories [Line Items]
Raw materials	$ 2,102,075	$ 1,767,642
Gross carrying amount [member]
Disclosure of inventories [Line Items]
Raw materials	2,181,890	1,831,140
Allowance for impairment losses [member]
Disclosure of inventories [Line Items]
Raw materials	$ (79,815)	$ (63,498)

Inventories - Cost of Inventories Recognized as an Expense (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Analysis of income and expense [abstract]
Cost of revenue	$ 17,957,568		$ 16,372,032	$ 15,057,605
Loss on abandonment	5,323		12,369	5,497
Allowance for (reversal of) inventory valuation and obsolescence loss	16,317		27,341	(13,070)
Cost of revenue	$ 17,979,208	$ 640,285	$ 16,411,742	$ 15,050,032

Non-current Financial Assets at Fair Value Through Other Comprehensive Income - Summary of Non-current Financial Assets at Fair Value Through Other Comprehensive Income (Detail) - TWD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financial assets at fair value through other comprehensive income [line items]
Designation of equity instruments	$ 262,007	$ 121,808
Foreign unlisted stocks [member]
Financial assets at fair value through other comprehensive income [line items]
Designation of equity instruments	38,534	38,534
Valuation adjustments [member]
Financial assets at fair value through other comprehensive income [line items]
Designation of equity instruments	$ 223,473	$ 83,274

Non-current Financial Assets at Fair Value Through Other Comprehensive Income - Additional Information (Detail)	Dec. 31, 2020 TWD ($)
Financial assets at fair value through other comprehensive income [abstract]
Financial assets at fair value through other comprehensive income were pledged	$ 0

Non-current Financial Assets at Fair Value Through Other Comprehensive Income - Summary Amounts recognized in other comprehensive income in relation to the financial assets at fair value through other comprehensive income (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Financial assets at fair value through other comprehensive income [abstract]
Foreign unlisted stocks	$ 140,199	$ 4,993	$ (52,549)	$ 85,022

Investments accounted for using equity method - Details of Investment in Associates (Detail) - TWD ($) $ in Thousands		12 Months Ended
	Apr. 08, 2019	Dec. 31, 2020	Dec. 31, 2019
Disclosure of associates [line items]
Carrying amount		$ 3,271,677	$ 3,392,910
JMC ELECTRONICS CO., LTD. [member]
Disclosure of associates [line items]
Carrying amount		$ 250,769	249,793
Shareholding ratio	10.00%
Unimos Shanghai [member]
Disclosure of associates [line items]
Principal place of business		Shanghai, PRC
Measurement method		Equity method
Carrying amount		$ 3,020,908	$ 3,143,117
Shareholding ratio		45.02%	45.02%
Nature of relationship		Strategic Investee

Investments accounted for using equity method - Additional Information (Detail) $ in Thousands		12 Months Ended
	Apr. 08, 2019 USD ($) shares	Dec. 31, 2019 TWD ($)	Dec. 31, 2020 TWD ($)
Disclosure of associates [line items]
Cash consideration from disposals of investment in associates		$ 1,180,179
Gain on disposal of investment in associates		973,609
Carrying amount of investment in associates		3,392,910	$ 3,271,677
Individually Immaterial Associates [member]
Disclosure of associates [line items]
Carrying amount of investment in associates		249,793	250,769
JMC ELECTRONICS CO., LTD. [member]
Disclosure of associates [line items]
Investment in associates at fair value		807,000	454,010
Number of common shares disposed \| shares	9,100,000
Percentage of ownership interest in associate	10.00%
Cash consideration from disposals of investment in associates	$ 1,180,179
Gain on disposal of investment in associates	$ 973,609
Carrying amount of investment in associates		$ 249,793	$ 250,769

Investments accounted for using equity method - Summarized Financial Information for Investment in Material Associates (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)	Dec. 31, 2020 USD ($)
Disclosure of associates [line items]
Current assets	$ 12,356,103		$ 11,762,346		$ 440,032
Non-current assets	22,724,711		22,543,541		809,285
Current liabilities	(5,725,631)		(5,018,861)		(203,904)
Non-current liabilities	(8,639,344)		(9,756,441)		$ (307,669)
Carrying amount	3,271,677		3,392,910
Revenue	23,011,381	$ 819,493	20,337,881	$ 18,480,027
Other comprehensive (loss) income, net of income tax	115,308	4,107	(127,266)	(32,829)
Total comprehensive income for the year, net of income tax	2,494,286	$ 88,828	2,381,308	1,292,995
Unimos Shanghai [member]
Disclosure of associates [line items]
Current assets	2,438,725		3,042,377
Non-current assets	3,905,089		3,499,819
Current liabilities	(618,949)		(459,502)
Non-current liabilities	(248,583)		(448,929)
Total net assets	5,476,282		5,633,765
Share in associate's net assets	2,465,651		2,536,558
Depreciable assets	533,139		584,441
Goodwill	22,118		22,118
Carrying amount	3,020,908		3,143,117
Revenue	1,739,880		1,584,648	1,334,196
Profit (loss) for the year from continuing operations	(246,220)		(352,008)	(629,303)
Other comprehensive (loss) income, net of income tax	0
Total comprehensive income for the year, net of income tax	(246,220)		(352,008)	(629,303)
Dividends received from the associate	0
Individually Immaterial Associates [member]
Disclosure of associates [line items]
Carrying amount	250,769		249,793
Profit (loss) for the year from continuing operations	14,833		63,838	41,933
Other comprehensive (loss) income, net of income tax	23,143		5,732	(2,687)
Total comprehensive income for the year, net of income tax	$ 37,976		$ 69,570	$ 39,246

Property, Plant and Equipment, Net - Summary of Property, Plant and Equipment, Net (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	$ 17,979,444		$ 16,819,621	$ 15,265,311
Effects on initial application of IFRS 16			(31,904)
Adjusted Balance On Property Plant And Equipment			16,787,717
Additions	4,133,615		4,896,656	4,945,570
Disposals	(19,358)		(25,785)	(14,716)
Reclassifications	0		26,618	0
Depreciation expenses	(4,098,993)		(3,695,815)	(3,376,579)
Impairment losses			(9,938)
Exchange adjustments	(22)		(9)	35
Ending Balance	17,994,686	$ 640,836	17,979,444	16,819,621
Land [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	452,738		452,738	452,738
Adjusted Balance On Property Plant And Equipment			452,738
Additions	0		0	0
Disposals	0		0	0
Reclassifications	0		0	0
Depreciation expenses	0		0	0
Ending Balance	452,738		452,738	452,738
Buildings [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	4,095,929		3,908,731	3,919,086
Adjusted Balance On Property Plant And Equipment			3,908,731
Additions	132,572		116,238	247,186
Disposals	0		0	0
Reclassifications	258,421		455,792	199,724
Depreciation expenses	(394,636)		(384,832)	(457,265)
Ending Balance	4,092,286		4,095,929	3,908,731
Machinery and equipment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	11,163,121		10,232,093	8,813,727
Adjusted Balance On Property Plant And Equipment			10,232,093
Additions	592,565		2,334,358	2,445,313
Disposals	(8,940)		(16,033)	(904)
Reclassifications	2,336,238		1,111,715	1,154,663
Depreciation expenses	(2,734,667)		(2,489,070)	(2,180,718)
Impairment losses			(9,938)
Exchange adjustments	(20)		(4)	12
Ending Balance	11,348,297		11,163,121	10,232,093
Tools [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	896,476		742,179	690,469
Adjusted Balance On Property Plant And Equipment			742,179
Additions	409,832		781,465	591,229
Disposals	(3,121)		(9,336)	(11,745)
Reclassifications	398,798		7,880	7,604
Depreciation expenses	(749,624)		(625,712)	(535,378)
Ending Balance	952,361		896,476	742,179
Other equipment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	434,791		413,988	420,572
Effects on initial application of IFRS 16			(31,904)
Adjusted Balance On Property Plant And Equipment			382,084
Additions	142,776		224,287	172,652
Disposals	(7,297)		(416)	(2,067)
Reclassifications	159,195		25,042	26,026
Depreciation expenses	(220,066)		(196,201)	(203,218)
Exchange adjustments	(2)		(5)	23
Ending Balance	509,397		434,791	413,988
Construction in progress and equipment to be inspected [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	936,389		1,069,892	968,719
Adjusted Balance On Property Plant And Equipment			1,069,892
Additions	2,855,870		1,440,308	1,489,190
Disposals	0		0	0
Reclassifications	(3,152,652)		(1,573,811)	(1,388,017)
Depreciation expenses	0		0	0
Ending Balance	639,607		936,389	1,069,892
Gross carrying amount [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	70,401,687		67,064,936	63,638,420
Ending Balance	73,187,794		70,401,687	67,064,936
Gross carrying amount [member] \| Land [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	452,738		452,738	452,738
Ending Balance	452,738		452,738	452,738
Gross carrying amount [member] \| Buildings [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	10,821,972		10,254,531	9,809,970
Ending Balance	11,212,129		10,821,972	10,254,531
Gross carrying amount [member] \| Machinery and equipment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	51,244,512		48,274,171	45,778,207
Ending Balance	53,246,474		51,244,512	48,274,171
Gross carrying amount [member] \| Tools [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	5,008,321		4,402,711	4,004,703
Ending Balance	5,451,547		5,008,321	4,402,711
Gross carrying amount [member] \| Other equipment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	1,937,755		2,610,893	2,624,083
Ending Balance	2,185,299		1,937,755	2,610,893
Gross carrying amount [member] \| Construction in progress and equipment to be inspected [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	936,389		1,069,892	968,719
Ending Balance	639,607		936,389	1,069,892
Accumulated depreciation and impairment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	(52,422,243)		(50,245,315)	(48,373,109)
Ending Balance	(55,193,108)		(52,422,243)	(50,245,315)
Accumulated depreciation and impairment [member] \| Land [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	0		0	0
Ending Balance	0		0	0
Accumulated depreciation and impairment [member] \| Buildings [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	(6,726,043)		(6,345,800)	(5,890,884)
Ending Balance	(7,119,843)		(6,726,043)	(6,345,800)
Accumulated depreciation and impairment [member] \| Machinery and equipment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	(40,081,391)		(38,042,078)	(36,964,480)
Ending Balance	(41,898,177)		(40,081,391)	(38,042,078)
Accumulated depreciation and impairment [member] \| Tools [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	(4,111,845)		(3,660,532)	(3,314,234)
Ending Balance	(4,499,186)		(4,111,845)	(3,660,532)
Accumulated depreciation and impairment [member] \| Other equipment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	(1,502,964)		(2,196,905)	(2,203,511)
Ending Balance	(1,675,902)		(1,502,964)	(2,196,905)
Accumulated depreciation and impairment [member] \| Construction in progress and equipment to be inspected [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance	0		0	0
Ending Balance	$ 0		$ 0	$ 0

Property, Plant and Equipment, Net - Capitalization Interest and Capitalization Interest Rate Applied Related to Property, Plant and Equipment (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of detailed information about property, plant and equipment [abstract]
Capitalization interest	$ 9,762	$ 15,114	$ 18,542
Capitalization interest rate applied	1.4909%	1.7822%	1.7582%

Leasing arrangements - leasee - summary of carrying amount of right-of-use assets and the depreciation expenses (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2020 USD ($)
Disclosure of quantitative information about right-of-use assets [line items]
Carrying amount	$ 859,069	$ 687,068	$ 30,594
Depreciation expenses	76,526	36,099
Land [member]
Disclosure of quantitative information about right-of-use assets [line items]
Carrying amount	636,261	669,967
Depreciation expenses	20,938	22,657
Buildings [member]
Disclosure of quantitative information about right-of-use assets [line items]
Carrying amount	19,044	15,043
Depreciation expenses	7,819	7,113
Machinery and equipment [member]
Disclosure of quantitative information about right-of-use assets [line items]
Carrying amount	203,249
Depreciation expenses	46,225	4,520
Others [member]
Disclosure of quantitative information about right-of-use assets [line items]
Carrying amount	515	2,058
Depreciation expenses	$ 1,544	$ 1,809

Leasing arrangements - leasee - Summary of profit and loss accounts relating to lease contracts (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Items affecting profit or loss
Interest expense on lease liabilities	$ 13,442	$ 14,349
Expense on short-term lease contracts	$ 202,782	$ 230,589

Leasing arrangements - leasee - Additional Information (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Statement [line items]
Additions to right of use asset	$ 261,798	$ 11,183
Payments of lease liabilities	$ 274,727	$ 273,709
Top of range [member]
Statement [line items]
Lease term	30 years
Bottom of range [member]
Statement [line items]
Lease term	2 years

Accounts payable - Summary of Accounts Payable (Detail) - TWD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Statement [LineItems]
Trade and other payables	$ 966,821	$ 819,548
Account payable [Member]
Statement [LineItems]
Trade and other payables	766,805	419,520
Estimated account payable [Member]
Statement [LineItems]
Trade and other payables	$ 200,016	$ 400,028

Other Payables - Summary of Other Payables (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)
Trade and other current payables [abstract]
Payables to contractors and equipment suppliers	$ 1,145,359		$ 972,770
Employees' compensation payable	332,080		338,356
Salaries and bonus payable	788,720		741,027
Pension payable	15,159		31,009
Directors' remuneration payable	16,604		16,918
Interest payable	1,958		889
Other expense payable	949,523		876,067
Other payables	$ 3,249,403	$ 115,719	$ 2,977,036

Long-term Bank Loans - Summary of Long-term Bank Loans (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2020 USD ($)
Disclosure of detailed information about borrowings [Line Items]
Bank loans	$ 7,733,565	$ 9,041,645
Less:Fee on syndicated bank loan	(17,223)	(24,355)
Less: Unamortized interest on government granted bank loans	(64,212)
Less: Current portion (fee included)	(748,353)	(748,419)	$ (26,651)
Syndicated bank loans, excluding current portion	6,985,212	8,293,226	$ 248,761
Long-term bank loans [Member]
Disclosure of detailed information about borrowings [Line Items]
Unused credit lines of long-term	$ 11,239,000	$ 1,800,000
Gross carrying amount [member]
Disclosure of detailed information about borrowings [Line Items]
Interest rate range		1.7895%
Gross carrying amount [member] \| Minimum [Member]
Disclosure of detailed information about borrowings [Line Items]
Interest rate range	0.65%		0.65%
Gross carrying amount [member] \| Maximum [Member]
Disclosure of detailed information about borrowings [Line Items]
Interest rate range	1.7895%		1.7895%
Gross carrying amount [member] \| Syndicated bank loans repayable from November 2018 to May 2023 [member]
Disclosure of detailed information about borrowings [Line Items]
Bank loans	$ 3,310,000	$ 9,066,000
Period and payment term	Borrowing period is from May 30, 2018 to May 30, 2023; interest is repayable monthly; principal is repayable semi-annually from November 30, 2018	Borrowing period is from May 30, 2018 to May 30, 2023; interest is repayable monthly; principal is repayable semi-annually from November 30, 2018
Gross carrying amount [member] \| Government granted bank loans from March 2020 To February 2030 [Member]
Disclosure of detailed information about borrowings [Line Items]
Bank loans	$ 4,505,000
Period and payment term	Borrowing period is from March 11, 2020 to February 15, 2030; interest is repayable monthly; principal is repayable monthly from March 15, 2023

Long-term Bank Loans - Additional Information (Detail) $ in Millions		3 Months Ended
	May 15, 2018 TWD ($) Bank	Mar. 31, 2020 TWD ($)
Maximum [Member]
Disclosure of detailed information about borrowings [Line Items]
Maturity of loan		ten years
Minimum [Member]
Disclosure of detailed information about borrowings [Line Items]
Maturity of loan		seven years
Syndicated loan [member]
Disclosure of detailed information about borrowings [Line Items]
Number of banks in syndicate \| Bank	11
Principal amount of loan	$ 12,000
Maturity of loan	five years
Government granted bank loans [Member]
Disclosure of detailed information about borrowings [Line Items]
Principal amount of loan		$ 12,144

Pensions - Additional Information (Detail) $ in Thousands	12 Months Ended
Pensions - Additional Information (Detail) $ in Thousands	Dec. 31, 2020 TWD ($) Unit	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Disclosure of defined benefit plans [Line Items]
Defined benefit plans expected contribution \| $	$ 26,261
Weighted average duration of defined benefit obligation	12 years 7 months 6 days
Defined benefit pension plan [Member]
Disclosure of defined benefit plans [Line Items]
Number of units accrued in first tranche	2
Duration of first tranche	First 15 years
Number of units accrued in second tranche	1
Duration of second tranche	Thereafter 15 years
Maximum number of units accruable under the pension plan	45
Benefit measurement period	6 months
Employer contribution percentage	2.00%
Defined contribution pension plan [member]
Disclosure of defined benefit plans [Line Items]
Employer contribution percentage	6.00%	6.00%
Pension costs under defined contribution pension plans \| $	$ 184,562	$ 187,502	$ 193,047

Pensions - Defined Benefit Plans Amounts Recognized in Statements of Financial Position (Detail) - TWD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Surplus (deficit) in plan [abstract]
Present value of defined benefit obligations	$ (943,391)	$ (901,159)
Fair value of plan assets	431,740	421,052
Net defined benefit liability	$ (511,651)	$ (480,107)	$ (520,765)	$ (478,526)

Pensions - Movements in Net Defined Benefit Liability (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	$ (480,107)	$ (520,765)	$ (478,526)
Current service cost	(263)	(332)	(382)
Interest (expense) income	(4,664)	(6,339)	(8,138)
Total	(485,034)	(527,436)	(487,046)
Return of plan assets (excluding the amount included in interest income or expense)	12,568	12,601	8,145
Financial assumption movement effect	(57,180)	(27,993)	(56,934)
Experience adjustments	(7,378)	36,308	(11,172)
Gain (loss) on remeasurement, net defined benefit liability (asset)	(51,990)	20,916	(59,961)
Pension fund contribution	25,373	26,413	26,242
Ending balance	(511,651)	(480,107)	(520,765)
Present Value of Defined Benefit Obligation [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	(901,159)	(910,081)	(838,543)
Current service cost	(263)	(332)	(382)
Interest (expense) income	(8,835)	(11,170)	(14,429)
Total	(910,257)	(921,583)	(853,354)
Financial assumption movement effect	(57,180)	(27,993)	(56,934)
Experience adjustments	(7,378)	36,308	(11,172)
Gain (loss) on remeasurement, net defined benefit liability (asset)	(64,558)	8,315	(68,106)
Paid pension	31,424	12,109	11,379
Ending balance	(943,391)	(901,159)	(910,081)
Fair Value of Plan Assets [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	421,052	389,316	360,017
Interest (expense) income	4,171	4,831	6,291
Total	425,223	394,147	366,308
Return of plan assets (excluding the amount included in interest income or expense)	12,568	12,601	8,145
Gain (loss) on remeasurement, net defined benefit liability (asset)	12,568	12,601	8,145
Pension fund contribution	25,373	26,413	26,242
Paid pension	(31,424)	(12,109)	(11,379)
Ending balance	$ 431,740	$ 421,052	$ 389,316

Pensions - Principal Actuarial Assumptions Used and Sensitivity Analysis of Present Value of Defined Benefit Obligation Effected by Changes of Principal Actuarial Assumptions (Detail)	Dec. 31, 2020	Dec. 31, 2018
Disclosure of sensitivity analysis for actuarial assumptions [abstract]
Discount rate	0.50%	1.00%
Future salary increases	3.50%	3.50%

Pensions - Sensitivity Analysis of Present Value of Defined Benefit Obligations Effected by Changes of Significant Actuarial Assumptions (Detail) - TWD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Actuarial assumption of discount rates [member]
Disclosure of sensitivity analysis for actuarial assumptions [Line Items]
Percentage increase in assumption	0.25%	0.25%
Effect on present value of defined benefit obligations due to increase in assumption	$ (29,114)	$ (27,993)
Percentage decrease in assumption	0.25%	0.25%
Effect on present value of defined benefit obligations due to decrease in assumption	$ 30,434	$ 29,284
Actuarial assumption of expected rates of salary increases [member]
Disclosure of sensitivity analysis for actuarial assumptions [Line Items]
Percentage increase in assumption	0.25%	0.25%
Effect on present value of defined benefit obligations due to increase in assumption	$ 29,471	$ 28,501
Percentage decrease in assumption	0.25%	0.25%
Effect on present value of defined benefit obligations due to decrease in assumption	$ (28,365)	$ (27,407)

Pensions - Analysis of Timing of the Future Pension Payment (Detail) $ in Thousands	Dec. 31, 2020 TWD ($)
Disclosure of net defined benefit liability (asset) [Line Items]
Defined benefit plan expected future pension payments	$ 359,212
Within 1 year [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Defined benefit plan expected future pension payments	35,066
1-2 years [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Defined benefit plan expected future pension payments	35,198
2-5 years [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Defined benefit plan expected future pension payments	122,969
5-10 years [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Defined benefit plan expected future pension payments	$ 165,979

Share-based Payments - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Compensation expenses	$ 822	$ 41,043
Restricted shares award agreement [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Restricted shares outstanding shares	0

Share-based Payments - Issuance of Restricted Shares (Detail) shares in Thousands	May 10, 2016 shares $ / shares	Jul. 21, 2015 shares $ / shares	Dec. 31, 2019
Disclosure of share based payments other than equity instrument [line items]
Grant date	May 10, 2016	July 21, 2015
Restricted shares award agreement [member]
Disclosure of share based payments other than equity instrument [line items]
Number of shares			0
Restricted shares award agreement [member] \| July 21, 2015 [member]
Disclosure of share based payments other than equity instrument [line items]
Type of arrangement		Restricted shares award agreement
Share price on grant date \| $ / shares		$ 36.1
Number of shares \| shares		15,752
Contract period		3 years
Vesting condition		Meet service and performance conditions
Restricted shares award agreement [member] \| May 10, 2016 [member]
Disclosure of share based payments other than equity instrument [line items]
Type of arrangement	Restricted shares award agreement
Share price on grant date \| $ / shares	$ 30.6
Number of shares \| shares	1,548
Contract period	3 years
Vesting condition	Meet service and performance conditions

Capital stock - Additional Information (Detail) $ / shares in Units, $ in Thousands, $ in Thousands			12 Months Ended
	Mar. 07, 2019 TWD ($)	Aug. 15, 2018 TWD ($) shares	Dec. 31, 2020 TWD ($) $ / shares shares	Dec. 31, 2018 shares	Dec. 31, 2020 USD ($) shares	Dec. 31, 2019 TWD ($)	Aug. 06, 2019 shares
Disclosure of classes of share capital [line items]
Ordinary shares par value \| $ / shares			$ 10
Number of shares outstanding			727,240,000		727,240,000
Percentage of capital reduction		15.00%
Amount of capital reduction \| $		$ 1,329,446
Authorised capital \| $			$ 9,700,000
Number of shares authorised			970,000,000		970,000,000
Paid in capital			$ 7,272,401		$ 258,989	$ 7,272,401
Approval for number of treasury stock cancelled							25,570,000
Cancellation of treasury stock \| $	$ 962,503
Top of range [member]
Disclosure of classes of share capital [line items]
Share buyback as a percentage of the companies issued shares			10.00%		10.00%	10.00%
Ordinary shares [member]
Disclosure of classes of share capital [line items]
Number of shares outstanding			85,412,000		85,412,000
Capital reduction		132,945,000		(128,422,000)
American depositary shares [member]
Disclosure of classes of share capital [line items]
Number of shares represented by each unit of ADS			20
Number of shares outstanding			4,270,600		4,270,600

Capital stock - Movement of Ordinary Shares Issued (Detail) - Ordinary shares [member] - shares shares in Thousands		12 Months Ended
	Aug. 15, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of classes of share capital [line items]
Beginning balance		727,240	727,265	856,059
Restricted shares – cancelled			(25)	(349)
Restricted shares – uncancelled				(23)
Capital reduction	132,945			(128,422)
Ending balance		727,240	727,240	727,265

Capital stock - Movement of Treasury Stock (Detail) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($) shares
Capital reduction	$ 1,284,223
Treasury stock [member]
Treasury stock shares at beginning balance \| shares	30,085
Capital reduction \| shares	(4,515)
Treasury stock shares at ending balance \| shares	25,570
Beginning balance	$ 1,007,654
Capital reduction	(45,151)
Ending balance	$ 962,503

Capital Surplus - Details of Capital Surplus (Detail) $ in Thousands, $ in Thousands		12 Months Ended
	Mar. 07, 2019 TWD ($)	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Statement [LineItems]
Beginning balance		$ 6,050,787
Share-based payments				$ 822	$ 41,043
Capital reduction					(1,284,223)
Cancellation of treasury stock	$ 962,503
Ending balance		6,050,787	$ 215,484	6,050,787
Capital surplus [member]
Statement [LineItems]
Beginning balance		6,050,787		6,263,553	6,271,448
Share-based payments				(412)	(7,967)
Capital reduction					72
Cancellation of treasury stock				(212,354)
Ending balance		6,050,787		6,050,787	6,263,553
Share premium [member] \| Capital surplus [member]
Statement [LineItems]
Beginning balance		5,674,242		5,873,743	5,873,743
Cancellation of treasury stock				(199,501)
Reclassifications		369,241
Ending balance		6,043,483		5,674,242	5,873,743
Employee restricted shares [member] \| Capital surplus [member]
Statement [LineItems]
Beginning balance		369,241		382,506	390,401
Share-based payments				(412)	(7,967)
Capital reduction					72
Cancellation of treasury stock				(12,853)
Reclassifications		(369,241)
Ending balance				369,241	382,506
Others [member] \| Capital surplus [member]
Statement [LineItems]
Beginning balance		7,304		7,304	7,304
Ending balance		$ 7,304		$ 7,304	$ 7,304

Retained Earnings - Details of Retained Earnings (Detail) - TWD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure of reserves within equity [abstract]
Legal reserve	$ 258,416	$ 110,308	$ 302,653
Special reserve	19,802
Cash dividend	$ 1,309,032	$ 872,718	$ 256,806
Cash dividend, cash distribution per share	$ 1.80	$ 1.20	$ 0.30

Other equity interest - Summary of Other Equity Interest (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Disclosure of Other Equity Interest [Line Items]
Ending balance	$ 19,802	$ 705
Financial statements translation differences of foreign operations [member]
Disclosure of Other Equity Interest [Line Items]
Beginning balance	(89,682)		$ 14,516	$ 65,593
Adjust Balance on Other Equity Interest				65,593
Currency translation differences - The company	28,352		(104,198)	(51,077)
Ending balance	(61,330)		(89,682)	14,516
Unrealized gain (loss) on valuation of financial assets at fair value through other comprehensive income [member]
Disclosure of Other Equity Interest [Line Items]
Beginning balance	66,386		106,898
Effect on initial application of IFRS 9				42,843
Adjust Balance on Other Equity Interest				42,843
Evaluation adjustment - The Company	140,199		(52,549)	85,022
Evaluation adjustment - Associates	22,925		5,093	(2,438)
Evaluation adjustment related tax - The Company	(34,794)		7,016	(18,529)
Disposal of investment accounted for using equity method			(72)
Ending balance	194,716		66,386	106,898
Unrealized gain on valuation of available -for-sale financial assets [member]
Disclosure of Other Equity Interest [Line Items]
Beginning balance				678
Effect on initial application of IFRS 9				(678)
Unearned employee awards [member]
Disclosure of Other Equity Interest [Line Items]
Beginning balance			(1,701)	(54,570)
Effect on initial application of IFRS 9				0
Adjust Balance on Other Equity Interest				(54,570)
Employee restricted shares - The company			1,701	52,869
Ending balance				(1,701)
Other reserves [member]
Disclosure of Other Equity Interest [Line Items]
Beginning balance	(23,296)		119,713	11,701
Effect on initial application of IFRS 9				42,165
Adjust Balance on Other Equity Interest				53,866
Currency translation differences - The company	28,352		(104,198)	(51,077)
Employee restricted shares - The company	140,199		1,701	52,869
Evaluation adjustment - The Company			(52,549)	85,022
Evaluation adjustment - Associates	22,925		5,093	(2,438)
Evaluation adjustment related tax - The Company	(34,794)		7,016	(18,529)
Disposal of investment accounted for using equity method			(72)
Ending balance	$ 133,386		$ (23,296)	$ 119,713

Revenue - Summary of Revenue From Contracts with Customers (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Receivables from contracts with customers [abstract]
Revenue from contracts with customers	$ 23,011,381	$ 20,337,881	$ 18,480,027

Revenue - Summary of Contract Assets and Liabilities (Detail) - TWD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019
Disclosure of contract assets and liabilities in relation to revenue [Abstract]
Contract assets	$ 389,016	$ 377,869	$ 299,835
Contract liabilities (Advance payments)		$ 1,231	$ 1,432

Revenue - Additional Information (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of major customers [abstract]
Revenue recognized in current reporting period related to carried-forward contract liabilities for performance obligation not satisfied in prior year	$ 565	$ 766

Other Income (Expenses), Net - Summary of Other Income (Expenses), Net (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Analysis of income and expense [abstract]
Gain on disposal of scrapped materials	$ 51,077		$ 43,652	$ 59,380
Royalty income	2,962		12,336	43,224
Gain on disposal of items purchased on behalf of others	30,140		15,080	31,268
Gain on disposal of property, plant and equipment, net	48,070		20,271	14,274
Insurance compensation income			10,435	147
Impairment loss on property, plant and equipment			(9,938)
Others	3,329		1,092	(779)
Other income (expenses), net	$ 135,578	$ 4,828	$ 92,928	$ 147,514

Interest income - Disclosure of interest income (Details) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Disclosure of Interest Income [Abstract]
Bank deposits	$ 25,547		$ 59,901	$ 49,051
Imputed interest from deposits	25
Financial assets at amortized cost	2,206		4,467	920
Interest income	$ 27,778	$ 989	$ 64,368	$ 49,971

Other Income - Summary of Other income (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Analysis of other income [Abstract]
Rental income	$ 10,260		$ 9,249	$ 7,819
Dividend income	3,229		585	571
Grant income	7,668		925
Other non-operating income (expenses), net	$ 21,157	$ 753	$ 10,759	$ 8,390

Other gains and losses - Summary of Other gains and losses (Details) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Disclosure of Other gains and losses [Abstract]
Foreign exchange gains (losses), net	$ (355,255)		$ (154,993)	$ 93,104
Reimbursement of ADSs service charge	2,101		4,292	13,269
Gain on valuation of financial assets at fair value through profit or loss	24,015		1,317	1,485
Others	5,872		970	6,851
Total	$ (323,267)	$ (11,512)	$ (148,414)	$ 114,709

Finance Costs - Summary of Finance Costs (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Analysis of Finance Costs [abstract]
Bank loans	$ 158,720		$ 171,840	$ 170,476
Lease liabilities	13,442		14,349
Lease obligations payable				482
Less: Amounts capitalized in qualifying assets	(9,762)		(15,114)	(18,542)
Interest expense	162,400		171,075	152,416
Finance expense	9,082		9,187	37,832
Finance costs	$ 171,482	$ 6,107	$ 180,262	$ 190,248

Expenses by nature - Summary of Expenses by nature (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Analysis of income and expense [abstract]
Raw materials and supplies used	$ 4,708,493	$ 3,575,283	$ 3,079,909
Employee benefit expenses	6,010,227	6,075,773	5,606,833
Depreciation expenses	4,175,519	3,731,914	3,376,579
Others	4,686,218	4,590,720	4,464,499
Total operating costs and expenses	$ 19,580,457	$ 17,973,690	$ 16,527,820

Employee benefit expenses - Summary of Employee benefit expenses (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Classes of employee benefits expense [abstract]
Salaries	$ 4,937,591	$ 5,114,790	$ 4,628,039
Director's remuneration	28,229	26,266	18,456
Labor and health insurance	396,796	422,106	406,111
Pension	189,489	194,173	201,567
Share-based payments		822	41,043
Other personnel expenses	458,122	317,616	311,617
Total Employee benefit expenses	$ 6,010,227	$ 6,075,773	$ 5,606,833

Employee benefit expenses - Additional Information (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of defined benefit plans [Line Items]
Accrued Employee Compensation	$ 332,080	$ 338,356	$ 199,027
Accrued Directors remuneration	$ 16,604	$ 16,918	$ 9,951
Defined benefit pension plan [Member]
Disclosure of defined benefit plans [Line Items]
Employees' compensation distribution rate	10.00%
Director remuneration rate no more than	0.50%

Income Tax Expense - Additional Information (Detail) - TWD ($) $ in Thousands		3 Months Ended
	Oct. 31, 2016	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Disclosure of income tax expense [Line Items]
Taxable temporary differences not recognized as deferred tax liaibility			$ 45,005	$ 180,395
Reduction of unappropriated retained earnings through capital transfer	$ 5,052,343
Income taxes paid (refund)		$ 138,941

Income Tax Expense - Major Components of Income Tax Expense (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Current income tax:
Current income tax on profits for the period	$ 636,876		$ 408,788	$ 326,057
Income tax on unappropriated retained earnings	105,665		74,540	28,165
Prior year income tax under (over) estimation	(133,923)		(5,016)	3,729
Total current income tax	608,618		478,312	357,951
Deferred income tax:
Relating to origination and reversal of temporary differences	(14,237)		35,367	101,441
Impact of change in tax rate				(2,774)
Total deferred income tax	(14,237)		35,367	98,667
Income tax expense	$ 594,381	$ 21,167	$ 513,679	$ 456,618

Income Tax Expense - Deferred Tax Charged to Other Comprehensive Income (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Income tax relating to components of other comprehensive income [abstract]
Unrealized gain (loss) on valuation of financial assets at fair value through other comprehensive income	$ 34,794		$ (7,016)	$ 17,005
Remeasurement of defined benefit obligations	(10,398)		4,183	(11,992)
Impact of change in tax rate				(887)
Total	$ 24,396	$ 869	$ (2,833)	$ 4,126

Income Tax Expense - Reconciliation of Income Tax Expense and Accounting Profit Before Income Tax (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Reconciliation of income tax expense and accounting profit before income tax [abstract]
Tax calculated based on profit before tax and statutory tax rate	$ 595,258		$ 606,917	$ 356,488
Effects from adjustments based on regulation	26,974		(162,924)	81,042
Temporary differences not recognized as deferred tax assets	(4)		(608)	(10,951)
Prior year income tax under (over) estimation	(133,923)		(5,016)	3,729
Income tax on unappropriated retained earnings	105,665		74,540	28,165
Impact of change in tax rate				(2,774)
Effect of different tax rates in countries in which the Group operates	411		770	919
Income tax expense	$ 594,381	$ 21,167	$ 513,679	$ 456,618

- Definition

The aggregate amount included in the determination of profit (loss) for the period in respect of current tax and deferred tax. [Refer: Current tax expense (income); Deferred tax expense (income)]

+ References + Details

Income Tax Expense - Details of Deferred Tax Assets (Liabilities) (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2017 TWD ($)
Disclosure of the detail of deferred tax assets and liabilities [line items]
Recognized in profit or loss	$ 14,237	$ (35,367)	$ (98,667)
Deferred tax assets	185,691	194,552	226,716	$ 6,613	$ 212,372
Deferred tax liabilities	(310,427)	(309,129)	(308,759)	$ (11,055)	$ (174,293)
Deferred tax assets unrealized loss on inventories [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance	12,700	7,232	9,132
Effects on initial application of IFRS 9 and IFRS 15			(770)
Recognized in profit or loss	3,263	5,468	(1,130)
Ending balance	15,963	12,700	7,232
Property, plant and equipment, deferred tax assets [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance	38,668	64,183	55,494
Recognized in profit or loss	(2,267)	(25,515)	8,689
Ending balance	36,401	38,668	64,183
Provisions [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance	5,600	12,396	21,643
Recognized in profit or loss	(2,922)	(6,796)	(9,247)
Ending balance	2,678	5,600	12,396
Deferred tax assets deferred revenue [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance	27,650	34,156	39,485
Recognized in profit or loss	(6,506)	(6,506)	(5,329)
Ending balance	21,144	27,650	34,156
Net defined benefit liability [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance	92,612	100,743	78,451
Recognized in profit or loss	(4,089)	(3,948)	7,889
Recognized in other comprehensive income	10,398	(4,183)	14,403
Ending balance	98,921	92,612	100,743
Unrealized exchange losses deferred tax assets [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance	17,296	3,575	8,167
Effects on initial application of IFRS 9 and IFRS 15			144
Recognized in profit or loss	(7,381)	13,721	(4,736)
Ending balance	9,915	17,296	3,575
Investment tax credit [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance		4,420
Recognized in profit or loss		(4,420)	4,420
Ending balance			4,420
Other [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance	26	11
Recognized in profit or loss	643	15	11
Ending balance	669	26	11
Deferred tax asset [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance	194,552	226,716	212,372
Effects on initial application of IFRS 9 and IFRS 15			(626)
Recognized in profit or loss	(19,259)	(27,981)	567
Recognized in other comprehensive income	10,398	(4,183)	14,403
Ending balance	185,691	194,552	226,716
Property, plant and equipment, deferred tax liabilities [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance	(288,980)	(281,594)	(174,293)
Recognized in profit or loss	33,496	(7,386)	(107,301)
Ending balance	(255,484)	(288,980)	(281,594)
Deferred tax liabilities, contract assets [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Effects on initial application of IFRS 9 and IFRS 15			(8,067)
Recognized in profit or loss			8,067
Financial assets at fair value through other comprehensive income [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance	(20,149)	(27,165)
Effects on initial application of IFRS 9 and IFRS 15			(8,636)
Recognized in other comprehensive income	(34,794)	7,016	(18,529)
Ending balance	(54,943)	(20,149)	(27,165)
Deferred tax liabilities [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance	(309,129)	(308,759)	(174,293)
Effects on initial application of IFRS 9 and IFRS 15			(16,703)
Recognized in profit or loss	33,496	(7,386)	(99,234)
Recognized in other comprehensive income	(34,794)	7,016	(18,529)
Ending balance	$ (310,427)	$ (309,129)	$ (308,759)

Earnings Per Share - Income and Share Data Used in Basic and Diluted EPS Computations (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($) $ / shares shares	Dec. 31, 2020 $ / shares	Dec. 31, 2019 TWD ($) $ / shares shares	Dec. 31, 2018 TWD ($) $ / shares shares
Basic earnings per share, amount after tax
Equity holders of the Company - Amount after tax \| $	$ 2,378,978		$ 2,508,574	$ 1,325,824
Diluted earnings per share, amount after tax
Equity holders of the Company - Amount after tax \| $	$ 2,378,978		$ 2,508,574	$ 1,325,824
Weighted average number of ordinary shares outstanding	727,240		727,111	802,725
Diluted earnings per share, weighted-average number of ordinary shares outstanding
Employees' compensations	9,668		9,879	7,626
Restricted shares			126	3,356
Weighted average number of ordinary shares outstanding	736,908		737,116	813,707
Ordinary shares [member]
Basic earnings per share
Equity holders of the Company - Earnings per share \| (per share)	$ 3.27	$ 0.12	$ 3.45	$ 1.65
Diluted earnings per share
Equity holders of the Company - Earnings per share \| (per share)	$ 3.23	$ 0.11	$ 3.40	$ 1.63

Supplementary Cash Flow Information - Partial Cash Paid for Investing Activities (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Statement of cash flows [abstract]
Purchase of property, plant and equipment	$ 4,133,615		$ 4,896,656	$ 4,945,570
Add: Beginning balance of payable to contractors and equipment suppliers	972,770		1,516,735	713,313
Add :Beginning balance of payable on lease				29,842
Less: Ending balance of payable to contractors and equipment suppliers	(1,145,359)		(972,770)	(1,516,735)
Less:Ending balance of payable on lease				(17,792)
Cash paid during the year	$ 3,961,026	$ 141,062	$ 5,440,621	$ 4,154,198

Changes in liabilities from financing activities - Reconciliation of Liabilities Arising from Financing Activities (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	$ 9,735,691	$ 9,790,610	$ 10,612,745
Effects on initial application of IFRS 16		884,275
Adjusted balance at January 1, 2019		10,674,885
Changes in cash flow from financing activities	(1,411,210)	(804,608)	(859,382)
Adjustment to right-of-use assets	249,030	(148,512)
Reclassification to payable on equipment from lease liabilities		(9,000)
Reclassification	20,000
Amortization of loan fees	7,581	8,577	37,247
Amortization Of Interest Expense	24,638	14,349
Ending balance	8,625,730	9,735,691	9,790,610
Long-term bank loans (include the current portion) [member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	9,041,645	9,789,518	9,642,021
Adjusted balance at January 1, 2019		9,789,518
Changes in cash flow from financing activities	(1,326,857)	(756,450)	110,250
Amortization of loan fees	7,581	8,577	37,247
Amortization Of Interest Expense	11,196
Ending balance	7,733,565	9,041,645	9,789,518
Short-term bank loans [member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance			969,353
Changes in cash flow from financing activities			(969,353)
Guarantee deposits [member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	1,095	1,092	1,371
Adjusted balance at January 1, 2019		1,092
Changes in cash flow from financing activities	575	3	(279)
Reclassification	20,000
Ending balance	21,670	1,095	$ 1,092
Lease liabilities [member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	692,951
Effects on initial application of IFRS 16		884,275
Adjusted balance at January 1, 2019		884,275
Changes in cash flow from financing activities	(84,928)	(48,161)
Adjustment to right-of-use assets	249,030	(148,512)
Reclassification to payable on equipment from lease liabilities		(9,000)
Amortization Of Interest Expense	13,442	14,349
Ending balance	$ 870,495	$ 692,951

Related Party Transactions - Summary of Names of Related Parties and Relationship (Detail)	12 Months Ended
	Dec. 31, 2020
Unimos Shanghai [member]
Disclosure of transactions between related parties [Line Items]
Relationship	Associate
JMC ELECTRONICS CO., LTD. [member]
Disclosure of transactions between related parties [Line Items]
Relationship	Associate

Related Party Transactions - Summary of Purchases of Materials (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
JMC ELECTRONICS CO., LTD. [member]
Disclosure of transactions between related parties [Line Items]
Purchases of materials	$ 0	$ 9	$ 132,494

Related Party Transactions - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)
Disclosure of transactions between related parties [Line Items]
Acquisition of investment in associate	$ 794,694
ChipMOS BVI and Unimos Shanghai [member]
Disclosure of transactions between related parties [Line Items]
Acquisition of investment in associate	$ 794,694

Related Party Transactions - Key Management Personnel Compensation (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of transactions between related parties [abstract]
Salaries and other short-term employee benefits	$ 186,854	$ 178,713	$ 151,095
Post-employment compensation	4,258	2,049	2,067
Share-based payments			6,763
Total key management personnel compensation	$ 191,112	$ 180,762	$ 159,925

Pledged assets - Certain Assets Provided as Collateral Mainly for Long-term Bank Loans and Leases (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Statement [LineItems]
Purpose	Lease and bank loan
Non-current financial assets at amortized cost	$ 48,319	$ 68,450
Assets pledged as collateral for liabilities	$ 11,505,888	8,723,029
Land [member]
Statement [LineItems]
Purpose	Bank loan
Property, plant and equipment, net	$ 452,738	452,738
Buildings [member]
Statement [LineItems]
Purpose	Bank loan
Property, plant and equipment, net	$ 4,092,287	4,095,929
Machinery and equipment [member]
Statement [LineItems]
Purpose	Bank loan
Property, plant and equipment, net	$ 6,912,544	$ 4,105,912

Significant contingent liabilities and unrecognized contract commitments - Additional Information (Detail) - TWD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Capital commitments [abstract]
Amount guaranteed by Bank of Taiwan	$ 99,000	$ 100,800

Significant contingent liabilities and unrecognized contract commitments - Capital Expenditures that are Contracted for, but not Provided for (Detail) - TWD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about property, plant and equipment [abstract]
Property plant and equipment, Contracted capital expenditures	$ 2,331,041	$ 1,640,712

Capital Management - Percentages of Liabilities to Assets Ratio Used for Monitoring Capital (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)
Disclosure of objectives, policies and processes for managing capital [abstract]
Total liabilities	$ 14,364,975	$ 511,573	$ 14,775,302
Total assets	$ 35,080,814	$ 1,249,317	$ 34,305,887
Liabilities to assets ratio	40.95%	40.95%	43.07%

Financial Risk Management and Fair Values of Financial Instruments - Summary of Loss Rate Methodology (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Contract assets [member]
Disclosure of detailed information about financial instruments [Line Items]
Expected loss rate	0.03%	0.03%
Total carrying amount	$ 389,133	$ 377,983
Loss allowance	$ (117)	$ (114)
Accounts receivable including related parties [member]
Disclosure of detailed information about financial instruments [Line Items]
Expected loss rate	0.03%	0.03%
Total carrying amount	$ 5,365,776	$ 4,455,300
Loss allowance	$ (1,620)	$ (1,351)
Other receivable including related parties [member]
Disclosure of detailed information about financial instruments [Line Items]
Expected loss rate	0.03%	0.03%
Total carrying amount	$ 51,446	$ 92,642
Loss allowance	$ (10)	$ (18)

Financial Risk Management and Fair Values of Financial Instruments - Summary of Natures of Assets and Liabilities (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about financial instruments [Line Items]
Financial assets at fair value through profit or loss	$ 63,488	$ 11,038
Financial assets at fair value	325,495	132,846
Foreign partnership interest [member] \| Recurring fair value measurement [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets at fair value through profit or loss	10,368	11,038
Foreign unlisted stocks [member] \| Recurring fair value measurement [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets at fair value through other comprehensive income	262,007	121,808
Listed stocks [member] \| Recurring fair value measurement [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets at fair value through profit or loss	53,120
Level 1 [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets at fair value	53,120
Level 1 [member] \| Listed stocks [member] \| Recurring fair value measurement [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets at fair value through profit or loss	53,120
Level 3 [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets at fair value	272,375	132,846
Level 3 [member] \| Foreign partnership interest [member] \| Recurring fair value measurement [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets at fair value through profit or loss	10,368	11,038
Level 3 [member] \| Foreign unlisted stocks [member] \| Recurring fair value measurement [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets at fair value through other comprehensive income	$ 262,007	$ 121,808

Financial Risk Management and Fair Values of Financial Instruments - Additional Information (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of detailed information about financial instruments [Line Items]
Realized and unrealized gain and loss arising from significant foreign exchange variation	$ (355,255)	$ (154,993)	$ 93,104
General increase or decrease of 100 basis points (1%) in interest rates [member]
Disclosure of detailed information about financial instruments [Line Items]
Estimated decrease or increase in the Group's profit and equity based on an increase or decrease in the interest rates	78,150	90,660	98,220
Equity price risk [member]
Disclosure of detailed information about financial instruments [Line Items]
Estimated decrease or increase in the Group's profit and equity based on an increase or decrease in the interest rates	$ 531	$ 0	$ 0
Adjustments to interest rate		1.00%

Financial Risk Management and Fair Values of Financial Instruments - Summary of Financial Instruments by Category (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)
Financial assets at fair value through profit or loss
Financial assets mandatorily measured at fair value through profit or loss	$ 63,488		$ 11,038
Financial assets at fair value through other comprehensive income
Designation of equity instruments	262,007		121,808
Financial assets at amortized cost
Cash and cash equivalents	4,113,651	$ 146,498	4,704,084
Financial assets at amortized cost	254,801		237,420
Notes receivable	599	21	765
Accounts receivable	5,364,156	191,031	4,452,904
Accounts receivable – related parties			1,045
Other receivables	51,436	1,832	89,676
Other receivables – related parties			2,948
Refundable deposits	21,186	754	21,145
Financial assets	10,131,324		9,642,833
Financial liabilities at amortized cost
Notes payable	2,899	103
Accounts payable	966,821	34,431	819,548
Other payables	3,249,403	115,719	2,977,036
Long-term bank loans (including current portion)	7,733,565		9,041,645
Guarantee deposits	21,670	$ 772	1,095
Financial liabilities	11,974,358		12,839,324
Lease liabilities (including current portion)	$ 870,495		$ 692,951

Financial Risk Management And Fair Values Of Financial Instruments - Summary of Effect of Profit or Loss or of Other Comprehensive Income from Financial Assets Categorized (Detail) - Financial instruments at fair value through other comprehensive income [member] - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items]
Favorable Changes	$ 5,325	$ 2,363
Unfavorable Changes In Fair Value	5,267	2,413
Enter prise value EBITDA multiple [member]
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items]
Favorable Changes	2,153	850
Unfavorable Changes In Fair Value	2,153	900
Discount for lack of marketability [member]
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items]
Favorable Changes	3,142	1,460
Unfavorable Changes In Fair Value	3,084	1,460
Foreign unlisted stocks [member] \| Price to book ratio multiple [member]
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items]
Favorable Changes	30	53
Unfavorable Changes In Fair Value	$ 30	$ 53

Financial Risk Management and Fair Values of Financial Instruments - Summary of Qualitative Information and Sensitivity Analysis of Changes in Significant Unobservable Inputs Under Valuation Model Used in Level Fair Value Measurement (Detail) - TWD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Non derivative equity instruments [member] \| Foreign unlisted stocks [member]
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items]
Fair value	$ 262,007,000	$ 121,808,000
Valuation technique	Comparable companies	Comparable companies
Non derivative equity instruments [member] \| Foreign unlisted stocks [member] \| Price book value multiple [member]
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items]
Range (weighted average method)	$ 1.97	$ 1.22
Relationship of inputs to fair value	The higher the multiple, the higher the fair value	The higher the multiple, the higher the fair value
Non derivative equity instruments [member] \| Foreign unlisted stocks [member] \| Enter prise value EBITDA multiple [member]
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items]
Range (weighted average method)	$ 12.00	$ 10.51
Relationship of inputs to fair value	The higher the multiple, the higher the fair value	The higher the multiple, the higher the fair value
Non derivative equity instruments [member] \| Foreign unlisted stocks [member] \| Discount for lack of marketability [member]
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items]
Range (weighted average method)	15.80%	15.80%
Relationship of inputs to fair value	The higher the discount for lack of marketability, the lower the fair value	The higher the discount for lack of marketability, the lower the fair value
Non derivative debt instruments [member] \| Foreign partnership interest [member]
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items]
Fair value	$ 10,368,000	$ 11,038,000
Valuation technique	Discounted cash flow	Discounted cash flow
Non derivative debt instruments [member] \| Foreign partnership interest [member] \| Discount rate [member]
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items]
Range (weighted average method)	0.30%	0.30%
Relationship of inputs to fair value	The lower the discount rate, the higher the fair value	The lower the discount rate, the higher the fair value

Financial Risk Management and Fair Values of Financial Instruments - Summary of Movements of Level 3 (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about financial instruments [Line Items]
Movement of financial instruments beginning balance	$ 132,846	$ 185,828
Gains or losses recognized in profit or loss Recorded as non-operating income (expenses)	(670)	(433)
Gains or losses recognized in other comprehensive gains (losses) Recorded as unrealized gains on valuation of financial assets at fair value through other comprehensive income	140,199	(52,549)
Movement of financial instruments ending balance	272,375	132,846
Debt instruments [member]
Disclosure of detailed information about financial instruments [Line Items]
Movement of financial instruments beginning balance	11,038	11,471
Gains or losses recognized in profit or loss Recorded as non-operating income (expenses)	(670)	(433)
Movement of financial instruments ending balance	10,368	11,038
Equity instruments [member]
Disclosure of detailed information about financial instruments [Line Items]
Movement of financial instruments beginning balance	121,808	174,357
Gains or losses recognized in other comprehensive gains (losses) Recorded as unrealized gains on valuation of financial assets at fair value through other comprehensive income	140,199	(52,549)
Movement of financial instruments ending balance	$ 262,007	$ 121,808

Financial Risk Management and Fair Values of Financial Instruments - Maturity Profile of Non-derivative Financial Liabilities Based on Contracted Undiscounted Payments (Detail) - TWD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Long-term bank loans	$ 8,091,523	$ 9,549,328
Lease liabilities	1,079,181	917,452	$ 1,184,183
Guarantee deposits	21,670	1,095
Total	9,192,374	10,467,875
Within 1 year [member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Long-term bank loans	846,401	914,159
Lease liabilities	145,594	36,806
Total	991,995	950,965
1 to 3 years [member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Long-term bank loans	3,558,597	1,786,842
Lease liabilities	160,146	60,111
Total	3,718,743	1,846,953
3 to 5 years [member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Long-term bank loans	2,198,717	6,848,327
Lease liabilities	54,689	57,836
Total	2,253,406	6,906,163
Over 5 years [member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Long-term bank loans	1,487,808
Lease liabilities	718,752	762,699
Guarantee deposits	21,670	1,095
Total	$ 2,228,230	$ 763,794

Financial Risk Management and Fair Values of Financial Instruments - Summary of Movements in Relation to Loss Allowance for Contract Assets, Accounts Receivable and Other Receivables (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of detailed information about financial instruments [Line Items]
Financial assets beginning balance	$ 9,642,833
Financial assets ending balance	10,131,324	$ 9,642,833
Contract assets [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets beginning balance	(114)	(135)
Adjustments for applying new standards			$ (115)
Provision for impairment loss	(3)		(20)
Reversal of impairment loss	0	21
Financial assets ending balance	(117)	(114)	(135)
Contract assets [member] \| IFRS 9 [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets beginning balance			(115)
Accounts receivable including related parties [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets beginning balance	(1,351)	(2,141)
Adjustments for applying new standards			(1,819)
Provision for impairment loss	(269)		(322)
Reversal of impairment loss	0	790
Financial assets ending balance	(1,620)	(1,351)	(2,141)
Accounts receivable including related parties [member] \| IFRS 9 [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets beginning balance			(1,819)
Other receivable including related parties [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets beginning balance	(18)	(13)
Adjustments for applying new standards			(7)
Provision for impairment loss	0	(5)	(7)
Reversal of impairment loss	8		1
Financial assets ending balance	$ (10)	$ (18)	(13)
Other receivable including related parties [member] \| IFRS 9 [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets beginning balance			$ (7)

- Definition

The amount of assets that are: (a) cash; (b) an equity instrument of another entity; (c) a contractual right: (i) to receive cash or another financial asset from another entity; or (ii) to exchange financial assets or financial liabilities with another entity under conditions that are potentially favourable to the entity; or (d) a contract that will, or may be, settled in the entity’s own equity instruments and is: (i) a non-derivative for which the entity is, or may be, obliged to receive a variable number of the entity’s own equity instruments; or (ii) a derivative that will, or may be, settled other than by the exchange of a fixed amount of cash or another financial asset for a fixed number of the entity’s own equity instruments. For this purpose the entity’s own equity instruments do not include puttable financial instruments classified as equity instruments in accordance with paragraphs 16A-16B of IAS 32, instruments that impose on the entity an obligation to deliver to another party a pro rata share of the net assets of the entity only on liquidation and are classified as equity instruments in accordance with paragraphs 16C-16D of IAS 32, or instruments that are contracts for the future receipt or delivery of the entity’s own equity instruments. [Refer: Financial instruments, class [member]; Financial liabilities]

+ References + Details

Financial Risk Management and Fair Values of Financial Instruments - Details of Exposure to Currency Risk Arising from Recognized Monetary Assets or Liabilities Denominated in a Currency Other Than Functional Currency (Detail) - Currency Risk [member] - TWD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financial assets, class [member] \| US$ [member]
Disclosure of nature and extent of risks arising from financial instruments [Line Items]
Change in exchange rate	5.00%	5.00%	5.00%
Financial assets, class [member] \| JPY [member]
Disclosure of nature and extent of risks arising from financial instruments [Line Items]
Change in exchange rate	5.00%	5.00%	5.00%
Financial assets, class [member] \| RMB [member]
Disclosure of nature and extent of risks arising from financial instruments [Line Items]
Change in exchange rate	5.00%	5.00%	5.00%
Financial liabilities, class [member] \| US$ [member]
Disclosure of nature and extent of risks arising from financial instruments [Line Items]
Change in exchange rate	5.00%	5.00%	5.00%
Financial liabilities, class [member] \| JPY [member]
Disclosure of nature and extent of risks arising from financial instruments [Line Items]
Change in exchange rate	5.00%	5.00%	5.00%
Profit and Loss [member] \| Financial assets, class [member] \| US$ [member]
Disclosure of nature and extent of risks arising from financial instruments [Line Items]
Effect of change in exchange rate	$ 250,396	$ 282,365	$ 261,492
Profit and Loss [member] \| Financial assets, class [member] \| JPY [member]
Disclosure of nature and extent of risks arising from financial instruments [Line Items]
Effect of change in exchange rate	1,901	3,682	2,470
Profit and Loss [member] \| Financial assets, class [member] \| RMB [member]
Disclosure of nature and extent of risks arising from financial instruments [Line Items]
Effect of change in exchange rate	1,497	1,334	1,979
Profit and Loss [member] \| Financial liabilities, class [member] \| US$ [member]
Disclosure of nature and extent of risks arising from financial instruments [Line Items]
Effect of change in exchange rate	37,608	11,793	27,997
Profit and Loss [member] \| Financial liabilities, class [member] \| JPY [member]
Disclosure of nature and extent of risks arising from financial instruments [Line Items]
Effect of change in exchange rate	$ 21,251	$ 14,261	$ 33,887

Financial Risk Management and Fair Values of Financial Instruments - Information on Assets and Liabilities Denominated in Foreign Currencies whose Values would be Materially Affected by Exchange Rate Fluctuations (Detail) ¥ in Thousands, ¥ in Thousands, $ in Thousands, $ in Thousands	Dec. 31, 2020 TWD ($) $ / JPY $ / USD $ / CNY	Dec. 31, 2020 USD ($) $ / JPY $ / USD $ / CNY	Dec. 31, 2020 JPY (¥) $ / JPY $ / USD $ / CNY	Dec. 31, 2020 CNY (¥) $ / JPY $ / USD $ / CNY	Dec. 31, 2019 TWD ($) $ / JPY $ / USD $ / CNY	Dec. 31, 2019 USD ($) $ / JPY $ / USD $ / CNY	Dec. 31, 2019 JPY (¥) $ / JPY $ / USD $ / CNY	Dec. 31, 2019 CNY (¥) $ / JPY $ / USD $ / CNY
Disclosure of detailed information about financial instruments [Line Items]
Assets denominated in foreign currencies \| $	$ 10,131,324				$ 9,642,833
Exchange rate	28.08	28.08	28.08	28.08
Currency Risk [member] \| US$ [member]
Disclosure of detailed information about financial instruments [Line Items]
Assets denominated in foreign currencies	$ 5,007,923	$ 175,840			5,647,303	$ 188,369
Liabilities denominated in foreign currencies	$ 752,157	$ 26,410			$ 235,853	$ 7,867
Currency Risk [member] \| US$ [member] \| Financial Liability [member]
Disclosure of detailed information about financial instruments [Line Items]
Exchange rate \| $ / USD	28.4800	28.4800	28.4800	28.4800	29.9800	29.9800	29.9800	29.9800
Currency Risk [member] \| US$ [member] \| Financial Asset [member]
Disclosure of detailed information about financial instruments [Line Items]
Exchange rate \| $ / USD	28.4800	28.4800	28.4800	28.4800	29.9800	29.9800	29.9800	29.9800
Currency Risk [member] \| JPY [member]
Disclosure of detailed information about financial instruments [Line Items]
Assets denominated in foreign currencies	$ 38,029		¥ 137,635		$ 73,642		¥ 266,819
Liabilities denominated in foreign currencies	$ 425,016		¥ 1,538,241		$ 285,217		¥ 1,033,394
Currency Risk [member] \| JPY [member] \| Financial Liability [member]
Disclosure of detailed information about financial instruments [Line Items]
Exchange rate \| $ / JPY	0.2763	0.2763	0.2763	0.2763	0.2760	0.2760	0.2760	0.2760
Currency Risk [member] \| JPY [member] \| Financial Asset [member]
Disclosure of detailed information about financial instruments [Line Items]
Exchange rate \| $ / JPY	0.2763	0.2763	0.2763	0.2763	0.2760	0.2760	0.2760	0.2760
Currency Risk [member] \| RMB [member]
Disclosure of detailed information about financial instruments [Line Items]
Assets denominated in foreign currencies	$ 29,930			¥ 6,838	$ 26,678			¥ 6,197
Currency Risk [member] \| RMB [member] \| Financial Asset [member]
Disclosure of detailed information about financial instruments [Line Items]
Exchange rate \| $ / CNY	4.3770	4.3770	4.3770	4.3770	4.3050	4.3050	4.3050	4.3050
Other Risks [Member] \| JPY [member]
Disclosure of detailed information about financial instruments [Line Items]
Assets denominated in foreign currencies	$ 262,007		¥ 948,270		$ 121,808		¥ 441,334
Other Risks [Member] \| JPY [member] \| Financial Asset [member]
Disclosure of detailed information about financial instruments [Line Items]
Exchange rate	0.2763	0.2763	0.2763	0.2763	0.2760	0.2760	0.2760	0.2760
Other Risks [Member] \| RMB [member]
Disclosure of detailed information about financial instruments [Line Items]
Assets denominated in foreign currencies	$ 3,020,908			¥ 690,178	$ 3,143,117	$ 730,108
Other Risks [Member] \| RMB [member] \| Financial Asset [member]
Disclosure of detailed information about financial instruments [Line Items]
Exchange rate \| $ / CNY	4.3770	4.3770	4.3770	4.3770	4.3050	4.3050	4.3050	4.3050

Segment Information - Financial Segment Information for Operating Segments (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Revenue
Revenue	$ 23,011,381	$ 819,493	$ 20,337,881	$ 18,480,027
Operating profit (loss)	3,566,502	$ 127,012	2,457,119	2,099,721
Interest expense	(162,400)		(171,075)	(152,416)
Purchase of property, plant and equipment	4,133,615		4,896,656	4,945,570
Continuing operations [member]
Revenue
Revenue	23,011,381		20,337,881	18,480,027
Operating profit (loss)	3,566,502		2,457,119	2,099,721
Depreciation expenses	(4,175,519)		(3,731,914)	(3,376,579)
Share of profit (loss) of associates	(147,329)		(154,926)	(300,101)
Interest income	27,778		64,368	49,971
Interest expense	(162,400)		(171,075)	(152,416)
Purchase of property, plant and equipment	4,133,615		4,896,656	4,945,570
Continuing operations [member] \| External [member]
Revenue
Revenue	23,011,381		20,337,881	18,480,027
Continuing operations [member] \| Operating segments [member] \| Testing [member]
Revenue
Revenue	5,002,730		4,257,800	4,790,097
Operating profit (loss)	1,333,682		709,142	1,306,742
Depreciation expenses	(853,829)		(802,740)	(769,660)
Purchase of property, plant and equipment	887,204		764,105	1,563,919
Continuing operations [member] \| Operating segments [member] \| Testing [member] \| External [member]
Revenue
Revenue	5,002,730		4,257,800	4,790,097
Continuing operations [member] \| Operating segments [member] \| Assembly [member]
Revenue
Revenue	6,001,964		5,148,877	4,679,676
Operating profit (loss)	67,730		(227,096)	(207,700)
Depreciation expenses	(523,341)		(521,311)	(578,205)
Purchase of property, plant and equipment	803,693		548,063	321,976
Continuing operations [member] \| Operating segments [member] \| Assembly [member] \| External [member]
Revenue
Revenue	6,001,964		5,148,877	4,679,676
Continuing operations [member] \| Operating segments [member] \| LCDD [member]
Revenue
Revenue	7,023,003		6,922,205	5,694,720
Operating profit (loss)	1,687,986		1,740,720	1,226,755
Depreciation expenses	(2,213,504)		(1,796,951)	(1,400,784)
Purchase of property, plant and equipment	2,143,401		3,077,806	2,732,141
Continuing operations [member] \| Operating segments [member] \| LCDD [member] \| External [member]
Revenue
Revenue	7,023,003		6,922,205	5,694,720
Continuing operations [member] \| Operating segments [member] \| Bumping [member]
Revenue
Revenue	4,983,684		4,008,999	3,315,534
Operating profit (loss)	487,323		232,404	(202,497)
Depreciation expenses	(578,890)		(604,553)	(627,412)
Purchase of property, plant and equipment	298,834		506,635	327,251
Continuing operations [member] \| Operating segments [member] \| Bumping [member] \| External [member]
Revenue
Revenue	4,983,684		4,008,999	3,315,534
Continuing operations [member] \| Operating segments [member] \| Others [member]
Revenue
Revenue	39,646		32,808	35,738
Operating profit (loss)	(10,230)		1,931	(23,433)
Depreciation expenses	(5,955)		(6,359)	(518)
Share of profit (loss) of associates	(320,578)		(370,351)	(668,377)
Interest income	27,778		64,368	49,971
Interest expense	(162,400)		(171,075)	(152,416)
Purchase of property, plant and equipment	483		47	283
Continuing operations [member] \| Operating segments [member] \| Others [member] \| Intersegment [member]
Revenue
Revenue	39,646		32,808	35,738
Continuing operations [member] \| Elimination [member]
Revenue
Revenue	(39,646)		(32,808)	(35,738)
Operating profit (loss)	11		18	(146)
Share of profit (loss) of associates	173,249		215,425	368,276
Continuing operations [member] \| Elimination [member] \| Intersegment [member]
Revenue
Revenue	$ (39,646)		$ (32,808)	$ (35,738)

Segment Information - Schedule of Information on Products and Services (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Disclosure of products and services [line items]
Net revenue	$ 23,011,381	$ 819,493	$ 20,337,881	$ 18,480,027
Percentage of total revenue	100.00%	100.00%	100.00%	100.00%
Testing [member]
Disclosure of products and services [line items]
Net revenue	$ 5,002,730		$ 4,257,800	$ 4,790,097
Percentage of total revenue	22.00%	22.00%	21.00%	26.00%
Assembly [member]
Disclosure of products and services [line items]
Net revenue	$ 6,001,964		$ 5,148,877	$ 4,679,676
Percentage of total revenue	26.00%	26.00%	25.00%	25.00%
LCDD [member]
Disclosure of products and services [line items]
Net revenue	$ 7,023,003		$ 6,922,205	$ 5,694,720
Percentage of total revenue	30.00%	30.00%	34.00%	31.00%
Bumping [member]
Disclosure of products and services [line items]
Net revenue	$ 4,983,684		$ 4,008,999	$ 3,315,534
Percentage of total revenue	22.00%	22.00%	20.00%	18.00%

- Definition

The income arising in the course of an entity's ordinary activities. Income is increases in assets, or decreases in liabilities, that result in increases in equity, other than those relating to contributions from holders of equity claims.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2020-01-01
-Paragraph 28
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2020-en-r&anchor=para_28_a&doctype=Standard
-URIDate 2020-01-01

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2020-01-01
-Paragraph 23
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2020-en-r&anchor=para_23_a&doctype=Standard
-URIDate 2020-01-01

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2020-01-01
-Paragraph 32
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2020-en-r&anchor=para_32&doctype=Standard
-URIDate 2020-01-01

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2020-01-01
-Paragraph 33
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2020-en-r&anchor=para_33_a&doctype=Standard
-URIDate 2020-01-01

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2020-01-01
-Paragraph 34
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2020-en-r&anchor=para_34&doctype=Standard
-URIDate 2020-01-01

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2020-01-01
-Paragraph 82
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_82_a&doctype=Standard
-URIDate 2020-01-01

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 1
-IssueDate 2020-01-01
-Paragraph 103
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_103&doctype=Standard
-URIDate 2020-01-01

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 1
-IssueDate 2020-01-01
-Paragraph 102
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_102&doctype=Standard
-URIDate 2020-01-01

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 5
-IssueDate 2020-01-01
-Paragraph 33
-Subparagraph b
-Clause i
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=5&code=ifrs-tx-2020-en-r&anchor=para_33_b_i&doctype=Standard
-URIDate 2020-01-01

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2020-01-01
-Paragraph B12
-Subparagraph b
-Clause v
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2020-en-r&anchor=para_B12_b_v&doctype=Appendix&subtype=B
-URIDate 2020-01-01

Reference 11: http://www.xbrl.org/2003/role/exampleRef
-Name IFRS
-Number 12
-IssueDate 2020-01-01
-Paragraph B10
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2020-en-r&anchor=para_B10_b&doctype=Appendix&subtype=B
-URIDate 2020-01-01

+ Details

Segment Information - Geographic Information of Revenue (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Disclosure of geographical areas [Line Items]
Revenue	$ 23,011,381	$ 819,493	$ 20,337,881	$ 18,480,027
ROC [member]
Disclosure of geographical areas [Line Items]
Revenue	18,341,726		15,875,027	14,751,766
Japan [member]
Disclosure of geographical areas [Line Items]
Revenue	1,291,026		1,905,032	1,825,479
Singapore [member]
Disclosure of geographical areas [Line Items]
Revenue	1,838,394		1,333,114	1,143,661
People's Republic of China ("PRC") [member]
Disclosure of geographical areas [Line Items]
Revenue	1,105,535		789,496	163,831
Others [member]
Disclosure of geographical areas [Line Items]
Revenue	$ 434,700		$ 435,212	$ 595,290

- Definition

+ References

+ Details

Segment Information - Schedule of Geographical Information (Detail) - TWD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Non-current assets [abstract]
Total non-current assets	$ 18,925,463	$ 18,733,638
ROC [member]
Non-current assets [abstract]
Total non-current assets	18,913,501	18,727,979
PRC [member]
Non-current assets [abstract]
Total non-current assets	117
Others [Member]
Non-current assets [abstract]
Total non-current assets	$ 11,845	$ 5,659

Segment Information - Net Revenue from Customers Representing at Least 10% of Total Revenue (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
Disclosure of major customers [Line Items]
Net revenue	$ 23,011,381	$ 819,493	$ 20,337,881	$ 18,480,027
Percentage of total revenue	100.00%	100.00%	100.00%	100.00%
Customer A [member]
Disclosure of major customers [Line Items]
Net revenue	$ 5,088,544		$ 4,756,755	$ 3,794,991
Percentage of total revenue	22.00%	22.00%	23.00%	21.00%
Customer X [member]
Disclosure of major customers [Line Items]
Net revenue	$ 2,660,866		$ 1,977,427	$ 1,328,752
Percentage of total revenue	12.00%	12.00%	10.00%	7.00%
Customer K [member]
Disclosure of major customers [Line Items]
Net revenue	$ 2,332,914		$ 2,419,612	$ 2,637,053
Percentage of total revenue	10.00%	10.00%	12.00%	14.00%
Customer C [member]
Disclosure of major customers [Line Items]
Net revenue	$ 2,143,130		$ 2,048,260	$ 1,957,467
Percentage of total revenue	9.00%	9.00%	10.00%	11.00%

- Definition

+ References

+ Details

Financial Statements Schedule: Valuation and Qualifying Accounts (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for Impairment of property, plant and equipment [member]
Disclosure of details of valuation and qualifying accounts [Line Items]
January 1	$ 193,340	$ 317,593	$ 320,455
Additions charged to expense or deduction of revenue		9,938
Deduction/Write-offs/Reversal	(11,338)	(134,191)	(2,862)
December 31	182,002	193,340	317,593
Allowance for Impairment of Obsolescence and Decline in Market Value of Inventories [Member]
Disclosure of details of valuation and qualifying accounts [Line Items]
January 1	63,498	36,157	53,714
Additions charged to expense or deduction of revenue	16,317	27,341
Deduction/Write-offs/Reversal			(17,557)
December 31	79,815	63,498	36,157
Provision for deficiency compensation [member]
Disclosure of details of valuation and qualifying accounts [Line Items]
January 1	1,998	29,352	57,155
Additions charged to expense or deduction of revenue	4,358	5,204	14,211
Deduction/Write-offs/Reversal	(2,893)	(32,558)	(42,014)
December 31	3,463	1,998	29,352
Sales for allowance [member]
Disclosure of details of valuation and qualifying accounts [Line Items]
January 1	26,000	32,627	70,156
Additions charged to expense or deduction of revenue	21,916	63,863	44,950
Deduction/Write-offs/Reversal	(38,052)	(70,490)	(82,479)
December 31	$ 9,864	$ 26,000	$ 32,627

Effects on initial application of IFRS 16 - Information About Differences Between Operating Lease Commitments And Lease Liabilities (Details) - TWD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Statement [LineItems]
Operating lease commitments disclosed by applying IAS 17 as of December 31, 2018				$ 320,214
Add: Lease payable recognized under finance lease by applying IAS 17 as of December 31, 2018				17,792
Less: Short-term leases				(28,121)
Add: Adjustments as a result of a different treatment of extension and termination options				874,298
Total lease contracts amount recognized as lease liabilities by applying IFRS 16 on January 1, 2019	$ 1,079,181	$ 917,452		$ 1,184,183
Lease liabilities recognized as of January 1, 2019 by applying IFRS 16	$ 870,495	$ 692,951
Bottom of range [member]
Statement [LineItems]
Incremental borrowing interest rate at the date of initial application			1.7895%	1.7895%
Top of range [member]
Statement [LineItems]
Incremental borrowing interest rate at the date of initial application			3.9474%	3.9474%
Effects of adopting new standards [member]
Statement [LineItems]
Lease liabilities recognized as of January 1, 2019 by applying IFRS 16				$ 884,275

Effects on initial application of IFRS 16 - Additional Information (Details) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019 TWD ($)	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Jan. 01, 2019 TWD ($)	Dec. 31, 2018
Statement [line items]
Right-of-use asset	$ 687,068	$ 859,069	$ 30,594
Lease liability	692,951	$ 870,495
Rent Expense	$ 28,126
Bottom of range [member]
Statement [line items]
Incremental borrowing interest rate				1.7895%	1.7895%
Top of range [member]
Statement [line items]
Incremental borrowing interest rate				3.9474%	3.9474%
Effects of adopting new standards [member]
Statement [line items]
Right-of-use asset				$ 898,387
Lease liability				884,275
Lease assets				31,904
Lease obligations payable				$ 17,792

Effects on Initial application of IFRS 9 - Additional Information (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Jan. 01, 2019 TWD ($)	Dec. 31, 2018 TWD ($)	Jan. 01, 2018 TWD ($)	Dec. 31, 2017 TWD ($)
Disclosure of initial application of standards or interpretations [line items]
Contract assets	$ 389,016		$ 377,869	$ 299,835
Retained earnings	5,401,569	$ 192,364	4,651,215
Deferred tax assets	$ 185,691	$ 6,613	$ 194,552		$ 226,716		$ 212,372
Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of initial application of standards or interpretations [line items]
Contract assets						$ (115)
Accounts receivable						(1,819)
Other receivables						(5)
Other receivables-related parties						(2)
Retained earnings						(1,940)
Deferred tax assets						$ 1

Effects on Initial application of IFRS 9 - Summary of Carrying Amount of Financial Assets Transferred (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Jan. 01, 2018 TWD ($)
Disclosure of financial assets [Line Items]
Measured at fair value through profit or loss	$ 63,488		$ 11,038
Measured at fair value through other comprehensive income	262,007		121,808
Measured at amortized cost	254,801		237,420
Financial assets	10,131,324		9,642,833
Retained earnings	$ 5,401,569	$ 192,364	$ 4,651,215
Fair value adjustment
Disclosure of financial assets [Line Items]
Measured at fair value through profit or loss				$ 493
Measured at fair value through other comprehensive income				50,801
Financial assets				51,294
Impairment loss adjustment [member]
Disclosure of financial assets [Line Items]
Measured at fair value through other comprehensive income				28,584
Financial assets				28,584
IAS 39 [member]
Disclosure of financial assets [Line Items]
Measured at cost				20,890
Other financial assets				70,241
Financial assets				91,131
IFRS 9 [member]
Disclosure of financial assets [Line Items]
Measured at fair value through profit or loss				11,433
Measured at fair value through other comprehensive income				89,335
Measured at amortized cost				70,241
Financial assets				171,009
Transferred into and measured at fair value through profit or loss [member]
Disclosure of financial assets [Line Items]
Measured at cost				(10,940)
Measured at fair value through profit or loss				10,940
Transferred into and measured at fair value through other comprehensive income [member]
Disclosure of financial assets [Line Items]
Measured at cost				(9,950)
Measured at fair value through other comprehensive income				9,950
Transfer into and measured at amortized cost [member]
Disclosure of financial assets [Line Items]
Other financial assets				(70,241)
Measured at amortized cost				70,241
Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of financial assets [Line Items]
Retained earnings				(1,940)
Increase (decrease) due to changes in accounting policy required by IFRSs [member] \| Fair value adjustment
Disclosure of financial assets [Line Items]
Retained earnings				493
Other equity interest				79,385
Increase (decrease) due to changes in accounting policy required by IFRSs [member] \| Impairment loss adjustment [member]
Disclosure of financial assets [Line Items]
Retained earnings				28,584
Other equity interest				(28,584)
Increase (decrease) due to changes in accounting policy required by IFRSs [member] \| Income tax adjustment [member]
Disclosure of financial assets [Line Items]
Other equity interest				(8,636)
Increase (decrease) due to changes in accounting policy required by IFRSs [member] \| IFRS 9 [member]
Disclosure of financial assets [Line Items]
Retained earnings				29,077
Other equity interest				$ 42,165

Effects on initial application of IFRS 9 - Summary of Carrying Amount of Financial Assets Transferred (Parenthetical) (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)	Jan. 01, 2018 TWD ($)	Dec. 31, 2017 TWD ($)
Disclosure of financial assets [Line Items]
Financial assets at amortized cost	$ 254,801		$ 237,420
Retained earnings	5,401,569	$ 192,364	4,651,215
Deferred tax liabilities	$ 310,427	$ 11,055	$ 309,129	$ 308,759		$ 174,293
Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of financial assets [Line Items]
Retained earnings					$ (1,940)
IAS 39 [member]
Disclosure of financial assets [Line Items]
Other financial assets					70,241
IFRS 9 [member]
Disclosure of financial assets [Line Items]
Financial assets at amortized cost					70,241
IFRS 9 [member] \| Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of financial assets [Line Items]
Retained earnings					29,077
Other equity interest					42,165
Financial assets at fair value through other comprehensive income, category [member] \| Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of financial assets [Line Items]
Retained earnings					28,584
Other equity interest					42,165
Deferred tax liabilities					8,636
Financial assets at fair value through other comprehensive income, category [member] \| IAS 39 [member]
Disclosure of financial assets [Line Items]
Available-for-sale financial assets					9,950
Financial assets at fair value through other comprehensive income, category [member] \| IFRS 9 [member]
Disclosure of financial assets [Line Items]
Available-for-sale financial assets					89,335
Financial assets at fair value through profit or loss, category [member] \| Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of financial assets [Line Items]
Retained earnings					493
Financial assets at fair value through profit or loss, category [member] \| IAS 39 [member]
Disclosure of financial assets [Line Items]
Available-for-sale financial assets					10,940
Financial assets at fair value through profit or loss, category [member] \| IFRS 9 [member]
Disclosure of financial assets [Line Items]
Available-for-sale financial assets					$ 11,433

Effects of initial application of IFRS 15 - Additional Information (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Jan. 01, 2019 TWD ($)	Dec. 31, 2018 TWD ($)	Jan. 01, 2018 TWD ($)	Dec. 31, 2017 TWD ($)
Disclosure of initial application of standards or interpretations [line items]
Retained earnings	$ 5,401,569	$ 192,364	$ 4,651,215
Inventories	2,102,075	74,860	1,767,642
Contract assets	389,016		377,869	$ 299,835
Provision for sales allowance	3,463	123	1,998
Deferred tax assets	185,691	6,613	194,552		$ 226,716		$ 212,372
Deferred tax liabilities	$ 310,427	$ 11,055	$ 309,129		$ 308,759		$ 174,293
Increase (decrease) due to application of IFRS 15 [member]
Disclosure of initial application of standards or interpretations [line items]
Retained earnings						$ (8,693)
Provision for sales allowance						70,156
Deferred tax assets						(626)
Deferred tax liabilities						8,067
Increase (decrease) due to application of IFRS 15 [member] \| Customized products [member]
Disclosure of initial application of standards or interpretations [line items]
Retained earnings						46,607
Inventories						(208,505)
Contract assets						$ 255,112