Formosa Sumco Technology Corporation — Proxy Solicitation & Information Statement 2026

May 11, 2026

Formosa SUMCO Technology Corporation
Notice of the 2026 Annual Shareholders’ Meeting

Time: 9:30 a.m., Thursday, June 11, 2026
Venue: No. 380, Section 6, Nanjing East Road, Taipei City
Means: Physical Shareholders’ Meeting

A. The agenda for the Meeting is as follows:

I. Report Items
1. 2025 Business Report.
2. Audit Committee’s Review Report on the 2025 Financial Statements.
3. Distribution of 2025 Employees Compensation.
4. Distribution of 2025 Cash Dividend.

II. Ratification Items
1. 2025 Business Report and Financial Statements.
2. Proposal for Distribution of 2025 Profits.

III. Discussion Items
1. Amendment of “Articles of Incorporation of the Company”. Please discuss and resolve.

IV. Extraordinary Motions

B. Notices for shareholders’ reference:

I. As for 2025 surplus earnings distribution, a cash dividend of NTD 1.0 per share has been proposed by the board of directors. The distribution date will be further decided by the time the approval is given in the shareholders’ meeting.

II. Shareholders are eligible to exercise voting rights electronically in the general meeting from May 11, 2026 to June 8, 2026. Please log in to “shareholder e-vote” webpage of TDCC to vote according to relevant instructions. (https://stockservices.tdcc.com.tw)

III. Registration time for the general meeting starts from 9:00 on June 11, 2026, and shareholders or proxies entrusted by the shareholders shall present the attendance certificates, attendance signature cards or other

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attendance identifications at the meeting. Solicitors of power of attorney shall bring identification documents for verification.

IV. The Company will compile all solicitation information from shareholder solicitation letters of attorney about the general meeting and transmit it to Securities & Futures Institute (SFI) as an electronic file on May 11, 2026. Shareholders are kindly requested to enter SFI website (https://free.sfi.org.tw) and click on “Free Enquiry System for Proxy Announcement Related Information”, and select “Entrance for inquiry of proxy announcement meeting information” on the right side. (Stock code of the Company: 3532)

V. Forms of notice of attendance and the proxy are separately attached. If a shareholder decides to attend the meeting personally, please sign or seal on the “Notice of Attendance” (no need to send back) and bring it to the shareholder’s meeting for attendance. If a shareholder entrusts a proxy to attend the meeting, please sign or seal on the power of attorney, fill in the name and address information of that proxy in person, and send it to the stock affairs team of the Company in five days before the meeting so as to further send the attendance card to the proxy.

VI. Stock affair team of the Company will be in charge of statistical verification of power of attorney.

VII. For proposal references and English version of the meeting notice / meeting handbook for the general meeting, please check out Market Observation Post System website (https://mops.twse.com.tw) for inquires. Route: Basic Information / Electronic Books / Shareholders’ meetings, and type in stock code “3532”, year “115” for inquires.

VIII. Hereby notified.

C. Notification:

I. For the amendment of contact address in this notice of attendance, please send to the Company before June 18, 2026 for further adjustment.

II. For shareholders who decide to attend the general meeting in person, please sign or seal on the notice of attendance. For shareholders who entrust a proxy to attend the meeting, please sign or seal on the power of attorney, fill in the name and address information of that proxy in person, and send it to the stock affairs team of the Company in five days before the meeting so as to further send the attendance card to the proxy.

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III. The cash dividend distribution date will be further decided after the approval is given in the shareholders' meeting. Cash dividends are distributed by remittance. Please check the bank account information in the “application form for registration of cash dividend remittance account” as attached, and only send back the application form with the amended bank account information and sealed to the Company before June 18, 2026 when the account information needs to be changed.

IV. For the meeting attendees who require to reapply for the attendance certificates, please directly make the application at the venue before the meeting begins.

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