3436 Q3 2025 Earnings Presentation

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3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION Results for Third Quarter of FY2025 (Ended September 30, 2025) November 11, 2025 SUMCO Corporation （Code：3436）（LEI：353800SUSRUOM0V6KU92） 1 3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION Notes Regarding the Forecasts This material is prepared for the purpose of continuous disclosure to general shareholders and investors and will not constitute an offer or solicitation of securities of the Company in any states or jurisdictions. The estimate, expectation, forecast and other future information is prepared based on the information which is available for the Company as of today and on certain assumptions and qualifications (which includes our subjective judgment) and the actual financial performance or result may be substantially different from such future information contained in the material due to risk factors including domestic and global economic conditions, trend of semiconductor market and foreign exchanges. 2

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3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION Results for Third Quarter of FY2025 (Ended September 30, 2025) November 11, 2025 SUMCO Corporation （Code：3436）（LEI：353800SUSRUOM0V6KU92） 1 3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION Notes Regarding the Forecasts This material is prepared for the purpose of continuous disclosure to general shareholders and investors and will not constitute an offer or solicitation of securities of the Company in any states or jurisdictions. The estimate, expectation, forecast and other future information is prepared based on the information which is available for the Company as of today and on certain assumptions and qualifications (which includes our subjective judgment) and the actual financial performance or result may be substantially different from such future information contained in the material due to risk factors including domestic and global economic conditions, trend of semiconductor market and foreign exchanges. 2

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3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION Contents ■ Summary and Market Environment ■ 3Q-2025 Consolidated Business Result Summary of Consolidated Business Result Analysis of Changes in Operating Profit Consolidated Balance Sheet and Consolidated Cash-Flow ■ 4Q-2025 Consolidated Business Forecast Consolidated Business Forecast Analysis of Changes in Operating Profit ■ Reference Materials 3 3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION Summary and Market Environment Mayuki Hashimoto Representative Director, CEO & Chairman of the Board 4

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3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION Contents ■ Summary and Market Environment ■ 3Q-2025 Consolidated Business Result Summary of Consolidated Business Result Analysis of Changes in Operating Profit Consolidated Balance Sheet and Consolidated Cash-Flow ■ 4Q-2025 Consolidated Business Forecast Consolidated Business Forecast Analysis of Changes in Operating Profit ■ Reference Materials 3 3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION Summary and Market Environment Mayuki Hashimoto Representative Director, CEO & Chairman of the Board 4

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3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION (Billions of Yen) 3Q-2025 3Q-2025 Forecast Actual Net Sales 101.0 99.1 (1.9) Operating Profit (3.5) (1.6) +1.9 Ordinary Profit (6.0) (2.6) +3.4 Profit (Note) (5.5) (3.9) +1.6 EBITDA margin (%) 25.7% 27.6% +1.8% Exchange Rate (Yen/US$) 145.0 147.1 +2.1 Change (Billions of Yen) 3Q-2025 4Q-2025 Actual Forecast Net Sales 99.1 100.0 +0.9 Operating Profit (1.6) (10.0) (8.4) Ordinary Profit (2.6) (13.0) (10.4) Profit (Note) (3.9) (16.0) (12.1) EBITDA margin (%) 27.6% 24.6% (3.0%) Exchange Rate (Yen/US$) 147.1 148.0 +0.9 Change 1-1. Summary ■ 3Q-2025 Consolidated Business Result ■ 4Q-2025 Consolidated Business Forecast (Note) Profit attributable to owners of parent 5 3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 1-2. Shareholder Return (Forecast) 6 Dividends are decided based on an overall consideration of profit levels, future outlook, funding needs for capital investment and other purposes, free cash flow, EBITDA, the status of dividend resources, and other factors. FY2021 (Dec-2021) FY2022 (Dec-2022) FY2023 (Dec-2023) FY2024 (Dec-2024) FY2025 (Dec-2025) Interim 17 36 42 15 10 Year-end 24 45 13 6 10 Total 41 81 55 21 20 Interim 4.9 12.6 14.7 5.2 3.5 Year-end 8.4 15.7 4.5 2.1 3.5 Total 13.3 28.3 19.2 7.3 7.0 Dividends per share for common stocks (Yen) Dividends payment (Billions of Yen)

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3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION (Billions of Yen) 3Q-2025 3Q-2025 Forecast Actual Net Sales 101.0 99.1 (1.9) Operating Profit (3.5) (1.6) +1.9 Ordinary Profit (6.0) (2.6) +3.4 Profit (Note) (5.5) (3.9) +1.6 EBITDA margin (%) 25.7% 27.6% +1.8% Exchange Rate (Yen/US$) 145.0 147.1 +2.1 Change (Billions of Yen) 3Q-2025 4Q-2025 Actual Forecast Net Sales 99.1 100.0 +0.9 Operating Profit (1.6) (10.0) (8.4) Ordinary Profit (2.6) (13.0) (10.4) Profit (Note) (3.9) (16.0) (12.1) EBITDA margin (%) 27.6% 24.6% (3.0%) Exchange Rate (Yen/US$) 147.1 148.0 +0.9 Change 1-1. Summary ■ 3Q-2025 Consolidated Business Result ■ 4Q-2025 Consolidated Business Forecast (Note) Profit attributable to owners of parent 5 3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 1-2. Shareholder Return (Forecast) 6 Dividends are decided based on an overall consideration of profit levels, future outlook, funding needs for capital investment and other purposes, free cash flow, EBITDA, the status of dividend resources, and other factors. FY2021 (Dec-2021) FY2022 (Dec-2022) FY2023 (Dec-2023) FY2024 (Dec-2024) FY2025 (Dec-2025) Interim 17 36 42 15 10 Year-end 24 45 13 6 10 Total 41 81 55 21 20 Interim 4.9 12.6 14.7 5.2 3.5 Year-end 8.4 15.7 4.5 2.1 3.5 Total 13.3 28.3 19.2 7.3 7.0 Dividends per share for common stocks (Yen) Dividends payment (Billions of Yen)

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3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 2-1. 200 mm Wafer Trend （Source： SUMCO’s estimation) 7 3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 2-2. 300 mm Wafer Trend （Source： SUMCO’s estimation) 8

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3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 2-1. 200 mm Wafer Trend （Source： SUMCO’s estimation) 7 3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 2-2. 300 mm Wafer Trend （Source： SUMCO’s estimation) 8

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3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 2-3. Market Environment ■ 3Q-2025  Volume - After a large increase in 2Q, 300 mm wafer shipments were mostly flat in 3Q. - Shipments remained slow for 200 mm wafers.  Pricing - Long-term contract prices were honored. ■ 4Q-2025 Forecast  Volume - 300 mm wafer outlook remains favorable for leading-edge products, driven by AI. As demand recovery for legacy products is slow, more time will be needed for customer inventory drawdown. - Shipments will continue to be slow for 200 mm wafers.  Pricing - Long-term contract prices are being maintained, while spot prices vary widely by region and application. ■ Outlook  The semiconductor market will see continued strong growth for AI use, and gradual recovery for other than AI.  The silicon wafer market can expect strong demand for 300 mm leading-edge wafers for logic chips and increased demand for 300 mm products for data center memory chips. Shipments of 200 mm and smaller wafers look to remain slow, with the ongoing shift to 300 mm wafers along with competition from China. 9 SUMCO CORPORATION 3Q-2025 Results Nov. 11, 2025 3. AI and Wafer Demand 1. Semiconductor Market Forecasts and AI-Related Semiconductor Growth 2. Increase in AI-Capable Smartphones and Wafer Demand 3. Increase in AI PCs/Tablets and Wafer Demand 4. Increase in AI Servers and Wafer Demand 5. Wafer Market Forecasts by Semiconductor Type 10

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3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 2-3. Market Environment ■ 3Q-2025  Volume - After a large increase in 2Q, 300 mm wafer shipments were mostly flat in 3Q. - Shipments remained slow for 200 mm wafers.  Pricing - Long-term contract prices were honored. ■ 4Q-2025 Forecast  Volume - 300 mm wafer outlook remains favorable for leading-edge products, driven by AI. As demand recovery for legacy products is slow, more time will be needed for customer inventory drawdown. - Shipments will continue to be slow for 200 mm wafers.  Pricing - Long-term contract prices are being maintained, while spot prices vary widely by region and application. ■ Outlook  The semiconductor market will see continued strong growth for AI use, and gradual recovery for other than AI.  The silicon wafer market can expect strong demand for 300 mm leading-edge wafers for logic chips and increased demand for 300 mm products for data center memory chips. Shipments of 200 mm and smaller wafers look to remain slow, with the ongoing shift to 300 mm wafers along with competition from China. 9 SUMCO CORPORATION 3Q-2025 Results Nov. 11, 2025 3. AI and Wafer Demand 1. Semiconductor Market Forecasts and AI-Related Semiconductor Growth 2. Increase in AI-Capable Smartphones and Wafer Demand 3. Increase in AI PCs/Tablets and Wafer Demand 4. Increase in AI Servers and Wafer Demand 5. Wafer Market Forecasts by Semiconductor Type 10

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SUMCO CORPORATION 3Q-2025 Results Nov. 11, 2025SUMCO CORPORATION 3-1. Semiconductor Market Forecasts and AI-Related Semiconductor Growth 0% 20% 40% 60% 80% 100% 0 200 400 600 800 1,000 1,200 2024 2025 2026 2027 2028 Semiconductor Market AI Semiconductor Market AI Ratio (Right Axis) (B$) CAGR(24-28) ： 11% 28% (Source: SUMCO estimates based on research companies' data) 11 SUMCO CORPORATION 3Q-2025 Results Nov. 11, 2025SUMCO CORPORATION 0 500 1,000 1,500 2024 2025 2026 2027 2028 Leading-edge Logic DRAM NAND ( k wafers / month ) 0 500 1,000 1,500 2,000 2024 2025 2026 2027 2028 No AI function With AI function (Million Units) 12 3-2. Increase in AI-Capable Smartphones and Wafer Demand Unit growth forecast Wafer demand forecast  Overall unit growth is slow at 2% annually, but 26% annual growth rate is seen for AI smartphones.  Wafer demand will increase gradually in line with unit growth rate. (Source: SUMCO estimates based on research companies' data)

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SUMCO CORPORATION 3Q-2025 Results Nov. 11, 2025SUMCO CORPORATION 3-1. Semiconductor Market Forecasts and AI-Related Semiconductor Growth 0% 20% 40% 60% 80% 100% 0 200 400 600 800 1,000 1,200 2024 2025 2026 2027 2028 Semiconductor Market AI Semiconductor Market AI Ratio (Right Axis) (B$) CAGR(24-28) ： 11% 28% (Source: SUMCO estimates based on research companies' data) 11 SUMCO CORPORATION 3Q-2025 Results Nov. 11, 2025SUMCO CORPORATION 0 500 1,000 1,500 2024 2025 2026 2027 2028 Leading-edge Logic DRAM NAND ( k wafers / month ) 0 500 1,000 1,500 2,000 2024 2025 2026 2027 2028 No AI function With AI function (Million Units) 12 3-2. Increase in AI-Capable Smartphones and Wafer Demand Unit growth forecast Wafer demand forecast  Overall unit growth is slow at 2% annually, but 26% annual growth rate is seen for AI smartphones.  Wafer demand will increase gradually in line with unit growth rate. (Source: SUMCO estimates based on research companies' data)

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SUMCO CORPORATION 3Q-2025 Results Nov. 11, 2025SUMCO CORPORATION 0 500 1,000 2024 2025 2026 2027 2028 Leading-edge Logic DRAM NAND ( k wafers / month ) 0 100 200 300 400 500 2024 2025 2026 2027 2028 No AI function With AI function (Million Units) 13  Overall unit growth will remain flat, but AI PCs/tablets will expand at 35% annually.  Wafer demand will maintain the same level despite the flattish unit growth and scaling effect. 3-3. Increase in AI PCs/Tablets sand Wafer Demand Unit growth forecast Wafer demand forecast (Source: SUMCO estimates based on research companies' data) SUMCO CORPORATION 3Q-2025 Results Nov. 11, 2025SUMCO CORPORATION 0 1,000 2,000 3,000 2024 2025 2026 2027 2028 Leading-edge Logic DRAM/HBM NAND ( k wafers / month ) 0 5 10 15 20 2024 2025 2026 2027 2028 AI servers General Servers (Million Units) 14  Continued high growth is expected for AI servers, which contain many semiconductors.  Demand for advanced semiconductors should drive strong growth in leading-edge wafers. 3-4. Increase in AI Servers and Wafer Demand Unit growth forecast Wafer demand forecast (Source: SUMCO estimates based on research companies' data)

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SUMCO CORPORATION 3Q-2025 Results Nov. 11, 2025SUMCO CORPORATION 0 500 1,000 2024 2025 2026 2027 2028 Leading-edge Logic DRAM NAND ( k wafers / month ) 0 100 200 300 400 500 2024 2025 2026 2027 2028 No AI function With AI function (Million Units) 13  Overall unit growth will remain flat, but AI PCs/tablets will expand at 35% annually.  Wafer demand will maintain the same level despite the flattish unit growth and scaling effect. 3-3. Increase in AI PCs/Tablets sand Wafer Demand Unit growth forecast Wafer demand forecast (Source: SUMCO estimates based on research companies' data) SUMCO CORPORATION 3Q-2025 Results Nov. 11, 2025SUMCO CORPORATION 0 1,000 2,000 3,000 2024 2025 2026 2027 2028 Leading-edge Logic DRAM/HBM NAND ( k wafers / month ) 0 5 10 15 20 2024 2025 2026 2027 2028 AI servers General Servers (Million Units) 14  Continued high growth is expected for AI servers, which contain many semiconductors.  Demand for advanced semiconductors should drive strong growth in leading-edge wafers. 3-4. Increase in AI Servers and Wafer Demand Unit growth forecast Wafer demand forecast (Source: SUMCO estimates based on research companies' data)

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SUMCO CORPORATION 3Q-2025 Results Nov. 11, 2025SUMCO CORPORATION 0 2,000 4,000 6,000 8,000 10,000 2024 2025 2026 2027 2028 Servers PCs/Tablets Smartphones Others ( k wafers / month ) 3-5. Wafer Market Forecasts by Semiconductor Type  In the medium term, as AI expands, the market will be driven by leading-edge wafers for servers.  Leading-edge logic will continue to grow, and memory is also expected to grow, driven by AI. 15 (Source: SUMCO estimates based on research companies' data) 3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 4-1. Customers’ 300 mm Wafer Inventory Trend （Source： SUMCO’s estimation) 16

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SUMCO CORPORATION 3Q-2025 Results Nov. 11, 2025SUMCO CORPORATION 0 2,000 4,000 6,000 8,000 10,000 2024 2025 2026 2027 2028 Servers PCs/Tablets Smartphones Others ( k wafers / month ) 3-5. Wafer Market Forecasts by Semiconductor Type  In the medium term, as AI expands, the market will be driven by leading-edge wafers for servers.  Leading-edge logic will continue to grow, and memory is also expected to grow, driven by AI. 15 (Source: SUMCO estimates based on research companies' data) 3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 4-1. Customers’ 300 mm Wafer Inventory Trend （Source： SUMCO’s estimation) 16

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3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 4-2. Customers’ 300 mm Wafer Inventory (Logic/Memory) （Source： SUMCO’s estimation) 17 3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 3Q-2025 Consolidated Business Result Shinichi Kubozoe Representative Director, Executive Vice President, Chief Financial Officer 18

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3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 4-2. Customers’ 300 mm Wafer Inventory (Logic/Memory) （Source： SUMCO’s estimation) 17 3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 3Q-2025 Consolidated Business Result Shinichi Kubozoe Representative Director, Executive Vice President, Chief Financial Officer 18

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3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 5-1. Summary of Consolidated Business Result 19 (Billions of Yen) 3Q-2024 3Q-2025 Actual (9 months) (9 months) 1Q 2Q 3Q Total Net sales 296.6 102.4 102.9 99.1 304.4 +7.8 Operating profit 29.9 5.9 1.5 (1.6) 5.8 (24.1) Non-operating income and expenses (3.9) (1.1) (1.6) (1.0) (3.7) +0.2 Ordinary profit 26.0 4.8 (0.1) (2.6) 2.1 (23.9) Income taxes (7.3) (1.2) (0.2) (0.9) (2.3) +5.0 Profit attributable to non-controlling interests (2.5) (0.6) 0.3 (0.4) (0.7) +1.8 Profit attributable to owners of parent 16.2 3.0 0.0 (3.9) (0.9) (17.1) Capital expenditure (Acceptance basis) 167.8 32.7 19.2 17.4 69.3 (98.5) Depreciation 56.1 22.7 26.7 30.6 80.0 +23.9 Operating depriciation 54.8 22.6 26.1 28.9 77.6 +22.8 EBITDA 84.8 28.6 27.5 27.3 83.4 (1.4) Exchange rate (Yen/US$) 151.8 153.9 145.2 147.1 148.7 (3.1) Operating margin (%) 10.1% 5.8% 1.4% (1.6%) 1.9% (8.2%) EBITDA margin (%) 28.6% 28.0% 26.7% 27.6% 27.4% (1.2%) ROE (%) 3.7% 1.8% (0.4%) (2.8%) (0.3%) (4.0%) Basic Earnings per share (Yen) 46.50 8.71 0.10 (11.66) (2.85) (49.35) *2. If the yen appreciates by 1 yen against the US dollar, operating profit of SUMCO will decrease by 1.2 billion yen per year *1. EBITDA = Operating profit + Operating Depreciation + Amortization of Goodwill Change (*1) (*2) (*1) (*2) 3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 5-2. Analysis of Changes in Operating Profit 1. 2Q-2025 Actual → 3Q-2025 Actual 2. 3Q-2024 Actual → 3Q-2025 Actual ¥3.1 billion Decrease ¥24.1 billion Decrease 20 (Billions of Yen) 2Q-2025 3Q-2025 Actual Actual Net Sales 102.9 99.1 (3.8) Operating Profit 1.5 (1.6) (3.1) Exchange Rate (Yen/US$) 145.2 147.1 +1.9 Change (Billions of Yen) 3Q-2024 3Q-2025 Act (9 months) Act (9 months) Net Sales 296.6 304.4 +7.8 Operating Profit 29.9 5.8 (24.1) Exchange Rate (Yen/US$) 151.8 148.7 (3.1) Change

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3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 5-1. Summary of Consolidated Business Result 19 (Billions of Yen) 3Q-2024 3Q-2025 Actual (9 months) (9 months) 1Q 2Q 3Q Total Net sales 296.6 102.4 102.9 99.1 304.4 +7.8 Operating profit 29.9 5.9 1.5 (1.6) 5.8 (24.1) Non-operating income and expenses (3.9) (1.1) (1.6) (1.0) (3.7) +0.2 Ordinary profit 26.0 4.8 (0.1) (2.6) 2.1 (23.9) Income taxes (7.3) (1.2) (0.2) (0.9) (2.3) +5.0 Profit attributable to non-controlling interests (2.5) (0.6) 0.3 (0.4) (0.7) +1.8 Profit attributable to owners of parent 16.2 3.0 0.0 (3.9) (0.9) (17.1) Capital expenditure (Acceptance basis) 167.8 32.7 19.2 17.4 69.3 (98.5) Depreciation 56.1 22.7 26.7 30.6 80.0 +23.9 Operating depriciation 54.8 22.6 26.1 28.9 77.6 +22.8 EBITDA 84.8 28.6 27.5 27.3 83.4 (1.4) Exchange rate (Yen/US$) 151.8 153.9 145.2 147.1 148.7 (3.1) Operating margin (%) 10.1% 5.8% 1.4% (1.6%) 1.9% (8.2%) EBITDA margin (%) 28.6% 28.0% 26.7% 27.6% 27.4% (1.2%) ROE (%) 3.7% 1.8% (0.4%) (2.8%) (0.3%) (4.0%) Basic Earnings per share (Yen) 46.50 8.71 0.10 (11.66) (2.85) (49.35) *2. If the yen appreciates by 1 yen against the US dollar, operating profit of SUMCO will decrease by 1.2 billion yen per year *1. EBITDA = Operating profit + Operating Depreciation + Amortization of Goodwill Change (*1) (*2) (*1) (*2) 3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 5-2. Analysis of Changes in Operating Profit 1. 2Q-2025 Actual → 3Q-2025 Actual 2. 3Q-2024 Actual → 3Q-2025 Actual ¥3.1 billion Decrease ¥24.1 billion Decrease 20 (Billions of Yen) 2Q-2025 3Q-2025 Actual Actual Net Sales 102.9 99.1 (3.8) Operating Profit 1.5 (1.6) (3.1) Exchange Rate (Yen/US$) 145.2 147.1 +1.9 Change (Billions of Yen) 3Q-2024 3Q-2025 Act (9 months) Act (9 months) Net Sales 296.6 304.4 +7.8 Operating Profit 29.9 5.8 (24.1) Exchange Rate (Yen/US$) 151.8 148.7 (3.1) Change

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3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION (Billions of Yen) Cash and deposits 95.6 76.0 (19.6) Notes and accounts receivable 92.5 84.8 (7.7) Finished goods and WIP 54.7 55.7 +1.0 Raw materials and supplies 178.5 188.2 +9.7 Tangible and intangible assets 699.6 691.0 (8.6) Deferred tax assets 9.3 8.8 (0.5) Other assets 42.4 38.0 (4.4) Total Assets 1,172.6 1,142.5 (30.1) Interest-bearing debt 353.9 359.4 +5.5 Other liabilities 161.5 133.7 (27.8) Total Liabilities 515.4 493.1 (22.3) Share capital 199.0 199.0 - Capital surplus 85.5 85.8 +0.3 Retained earnings 277.8 271.3 (6.5) Non-controlling interests etc. 94.9 93.3 (1.6) Total Net Assets 657.2 649.4 (7.8) Equity-to-asset ratio (%) 50.5% 51.0% +0.5% Net assets per share (Yen) 1,693.2 1,667.1 (26.0) D/E ratio (gross) 0.60x 0.62x +0.02x D/E ratio (net) 0.44x 0.49x +0.05x ChangeEnd of Dec-2024 End of Sep-2025 (Billions of Yen) 3Q-2025 (9months) Profit before income taxes 2.1 Depreciation 80.0 Subtotal 82.1 Decrease (increase) in inventories (8.4) Others, net 4.8 Net cash provided by operating activities 78.5 Capital expenditure (Acceptance basis) (69.3) Others, net (24.4) Net cash used in investing activities (93.7) Free cash-flow (15.2) Dividends paid (7.5) Net proceeds from borrowings 4.2 Effect of exchange rate change and others (1.1) Net increase (decrease) in cash and cash equivalents (19.6) Cash flow from financing activities, etc. 5-3. Balance Sheet and Cash-Flow (Consolidated) 1. Consolidated Balance Sheet 2. Consolidated Cash-Flow 21 3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 4Q-2025 Consolidated Business Forecast 22

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3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION (Billions of Yen) Cash and deposits 95.6 76.0 (19.6) Notes and accounts receivable 92.5 84.8 (7.7) Finished goods and WIP 54.7 55.7 +1.0 Raw materials and supplies 178.5 188.2 +9.7 Tangible and intangible assets 699.6 691.0 (8.6) Deferred tax assets 9.3 8.8 (0.5) Other assets 42.4 38.0 (4.4) Total Assets 1,172.6 1,142.5 (30.1) Interest-bearing debt 353.9 359.4 +5.5 Other liabilities 161.5 133.7 (27.8) Total Liabilities 515.4 493.1 (22.3) Share capital 199.0 199.0 - Capital surplus 85.5 85.8 +0.3 Retained earnings 277.8 271.3 (6.5) Non-controlling interests etc. 94.9 93.3 (1.6) Total Net Assets 657.2 649.4 (7.8) Equity-to-asset ratio (%) 50.5% 51.0% +0.5% Net assets per share (Yen) 1,693.2 1,667.1 (26.0) D/E ratio (gross) 0.60x 0.62x +0.02x D/E ratio (net) 0.44x 0.49x +0.05x ChangeEnd of Dec-2024 End of Sep-2025 (Billions of Yen) 3Q-2025 (9months) Profit before income taxes 2.1 Depreciation 80.0 Subtotal 82.1 Decrease (increase) in inventories (8.4) Others, net 4.8 Net cash provided by operating activities 78.5 Capital expenditure (Acceptance basis) (69.3) Others, net (24.4) Net cash used in investing activities (93.7) Free cash-flow (15.2) Dividends paid (7.5) Net proceeds from borrowings 4.2 Effect of exchange rate change and others (1.1) Net increase (decrease) in cash and cash equivalents (19.6) Cash flow from financing activities, etc. 5-3. Balance Sheet and Cash-Flow (Consolidated) 1. Consolidated Balance Sheet 2. Consolidated Cash-Flow 21 3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 4Q-2025 Consolidated Business Forecast 22

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3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 6-1. 4Q-2025 Consolidated Business Forecast 23 (Billions of Yen) Total Net sales 396.6 102.4 102.9 99.1 100.0 404.4 +7.8 Operating profit 36.9 5.9 1.5 (1.6) (10.0) (4.2) (41.1) Non-operating income and expenses 0.5 (1.1) (1.6) (1.0) (3.0) (6.7) (7.2) Ordinary profit 37.4 4.8 (0.1) (2.6) (13.0) (10.9) (48.3) Extraordinary income and losses (5.8) - - - - - +5.8 Income taxes (8.3) (1.2) (0.2) (0.9) (2.9) (5.2) +3.1 Profit attributable to non-controlling interests (3.5) (0.6) 0.3 (0.4) (0.1) (0.8) +2.7 Profit attributable to owners of parent 19.8 3.0 0.0 (3.9) (16.0) (16.9) (36.7) Depreciation 78.9 22.7 26.7 30.6 36.8 116.8 +37.9 Operating depriciation 77.1 22.6 26.1 28.9 34.6 112.2 +35.1 EBITDA 114.0 28.6 27.5 27.3 24.6 108.0 (6.0) Exchange rate (Yen/US$) 151.1 153.9 145.2 147.1 148.0 148.5 (2.6) Operating margin (%) 9.3% 5.8% 1.4% (1.6%) (10.0%) (1.0%) (10.3%) EBITDA margin (%) 28.8% 28.0% 26.7% 27.6% 24.6% 26.7% (2.1%) ROE (%) 3.4% 1.8% (0.4%) (2.8%) (11.1%) (2.9%) (6.3%) Basic Earnings per share (Yen) 56.84 8.71 0.10 (11.66) (45.48) (48.33) (105.17) 1Q ACT 2Q ACT 3Q ACT 4Q FCST *1 . If the yen appreciates by 1 yen against the US dollar, operating profit of SUMCO will decrease by 1.2 billion yen per year. FY 2024 Actual FY2025 Forecast Change (*1) (*1) 3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION (Billions of Yen) FY2024 FY2025 Actual Forecast Net Sales 396.6 404.4 +7.8 Operating Profit 36.9 (4.2) (41.1) Exchange Rate (Yen/US$) 151.1 148.5 (2.6) Change 6-2. Analysis of Changes in Operating Profit 1. 3Q-2025 Actual → 4Q-2025 Forecast ¥8.4 billion Decrease ¥41.1 billion Decrease 2. 2024 Actual (12 months) → 2025 Forecast (12 months) 24 (Billions of Yen) 3Q-2025 4Q-2025 Actual Forecast Net Sales 99.1 100.0 +0.9 Operating Profit (1.6) (10.0) (8.4) Exchange Rate (Yen/US$) 147.1 148.0 +0.9 Change

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3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION 6-1. 4Q-2025 Consolidated Business Forecast 23 (Billions of Yen) Total Net sales 396.6 102.4 102.9 99.1 100.0 404.4 +7.8 Operating profit 36.9 5.9 1.5 (1.6) (10.0) (4.2) (41.1) Non-operating income and expenses 0.5 (1.1) (1.6) (1.0) (3.0) (6.7) (7.2) Ordinary profit 37.4 4.8 (0.1) (2.6) (13.0) (10.9) (48.3) Extraordinary income and losses (5.8) - - - - - +5.8 Income taxes (8.3) (1.2) (0.2) (0.9) (2.9) (5.2) +3.1 Profit attributable to non-controlling interests (3.5) (0.6) 0.3 (0.4) (0.1) (0.8) +2.7 Profit attributable to owners of parent 19.8 3.0 0.0 (3.9) (16.0) (16.9) (36.7) Depreciation 78.9 22.7 26.7 30.6 36.8 116.8 +37.9 Operating depriciation 77.1 22.6 26.1 28.9 34.6 112.2 +35.1 EBITDA 114.0 28.6 27.5 27.3 24.6 108.0 (6.0) Exchange rate (Yen/US$) 151.1 153.9 145.2 147.1 148.0 148.5 (2.6) Operating margin (%) 9.3% 5.8% 1.4% (1.6%) (10.0%) (1.0%) (10.3%) EBITDA margin (%) 28.8% 28.0% 26.7% 27.6% 24.6% 26.7% (2.1%) ROE (%) 3.4% 1.8% (0.4%) (2.8%) (11.1%) (2.9%) (6.3%) Basic Earnings per share (Yen) 56.84 8.71 0.10 (11.66) (45.48) (48.33) (105.17) 1Q ACT 2Q ACT 3Q ACT 4Q FCST *1 . If the yen appreciates by 1 yen against the US dollar, operating profit of SUMCO will decrease by 1.2 billion yen per year. FY 2024 Actual FY2025 Forecast Change (*1) (*1) 3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION (Billions of Yen) FY2024 FY2025 Actual Forecast Net Sales 396.6 404.4 +7.8 Operating Profit 36.9 (4.2) (41.1) Exchange Rate (Yen/US$) 151.1 148.5 (2.6) Change 6-2. Analysis of Changes in Operating Profit 1. 3Q-2025 Actual → 4Q-2025 Forecast ¥8.4 billion Decrease ¥41.1 billion Decrease 2. 2024 Actual (12 months) → 2025 Forecast (12 months) 24 (Billions of Yen) 3Q-2025 4Q-2025 Actual Forecast Net Sales 99.1 100.0 +0.9 Operating Profit (1.6) (10.0) (8.4) Exchange Rate (Yen/US$) 147.1 148.0 +0.9 Change

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3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION Reference Materials 25 3Q-2025 Results Nov. 11, 2025 SUMCO CORPORATION ■ Depreciation and Capital Expenditure FCST 26  Capital expenditure has peaked in FY2023.  Depreciation expenses are expected to reach a peak in FY2026. Depreciation and Capex(Billions of Yen) (11-month period) (outlook)

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