SiC Wafer 8-Inch Transition: A Substrate Market Split in Two

If you buy SiC wafers, the substrate market you face today is not one market. Six-inch has been driven down by oversupply into what is, in effect, a commoditized market; eight-inch has only just entered volume production and has not yet formed a standard market price at all. Between the two, the supplier landscape is being redrawn at speed — the largest US substrate maker has come out the other side of bankruptcy protection, and Korea's only dedicated SiC substrate affiliate entered liquidation in July 2026. This is a phase in which comparing the numbers on quotations is no longer enough to read the market.

The problem: six-inch has a price, eight-inch does not

The six-inch substrate price trajectory looks like this.

The July 2026 rebound reports say supply has tightened and premiums have started to attach to incremental volume, but no specific price figures were published. As an aside: the widely repeated claim that six-inch substrates once sold "around $1,500" before the collapse circulates broadly in the industry, but we could not confirm a primary source for that figure, so we do not use it as a baseline.

Eight-inch is a different situation — public price information simply stops. Piecing together TrendForce-affiliated reports, average quotes in China went from $3,000–4,000 at the end of 2023 to about $2,000 in Q2 2024 — halving in six months — and were estimated at around $1,000 in Q1 2025. There is no published price after that. The consistent account in those same sources is that eight-inch is still in pilot production and a standard market price has not formed, and we likewise could not confirm actual 2026 eight-inch transaction prices from any public source. In practice, that means there is no market baseline to compare a quotation against.

Why it happened: Chinese oversupply and the flight to eight-inch

What broke the six-inch price

China added substrate capacity far faster than demand grew. According to digitimes tallies (Oct 2024), China's annual SiC substrate capacity expanded as follows.

On the 2025 projection, that is more than an eightfold build-out in three years. Demand did not keep pace — per Yole (Dec 2025), 2025 upstream (substrate and epi) utilization ran at about 50% and device lines at about 70%, and with the EV slowdown layered on top, Yole expects the downturn to last through 2027–2028. The result: global N-type substrate revenue in 2024 was $1.04 billion, down 9% year over year (TrendForce, May 2025). Capacity exploded while the market itself shrank. The EV slowdown shows up in device-maker results too — STMicroelectronics' 2025 annual revenue was $11.80 billion, down 11.1% from the prior year (ST annual report, 2026). The broader picture of how China's six-inch build-out pressures prices is covered in our 2026 SiC market outlook.

The market-share map has already shifted. On TrendForce's May 2025 figures, Wolfspeed led 2024 N-type substrate revenue at 33.7%, but the top two Chinese substrate makers combined for 34.4% — already matching Wolfspeed. The top four suppliers (two of them Chinese) held 82% between them. On a capacity basis, Chinese players account for roughly 40% of SiC wafer and epiwafer capacity (Yole, Dec 2025). Nor is Chinese material confined to the low end — in May 2023, Infineon signed long-term supply agreements with two Chinese substrate makers, starting at 150mm with a second phase planned at 200mm. A Western IDM formally bringing Chinese substrates into its qualified supply chain.

The move to eight-inch, and how fast it is actually going

With six-inch pushed to near cost, the Western, Japanese, and Korean camps are moving to eight-inch (200mm). The wafer area grows about 78%, and counting the reduced edge loss, die count rises about 85% (Power Electronics News). But the same source is explicit that the per-die saving is not immediate — for a 1.2kV/100A MOSFET, 200mm per-die cost is projected to come in about 20% below 150mm over five to seven years, and in the early phase of the transition there is no saving at all, because of substrate prices and process immaturity.

The major players' 200mm timelines:

Mitsubishi Electric (a planned new fab in Kumamoto) and Rohm (its Miyazaki site) have also announced eight-inch plans, but we could not confirm their status as of 2026 from primary sources, so we have left them out of the table. China has entered eight-inch as well — the joint venture ST established in China with a local partner (total investment $3.2 billion) began volume production in Q4 2025, targeting 10,000 automotive-grade eight-inch wafers per week at full ramp (TrendForce, Mar 2025). Chinese players are going further, unveiling 12-inch and even 14-inch prototypes in quick succession to pull the format race forward (TrendForce, Mar 2026).

The transition is nonetheless running behind early expectations. Industry forecasts from around 2023–2024 saw eight-inch reaching roughly 15% of shipments by 2026, but TrendForce's May 2025 forecast puts the point at which eight-inch exceeds 20% of total shipments at 2030. Yole likewise expects the eight-inch platform to drive the market only in the regrowth phase, after 2027–2028. Why eight-inch is hard comes down, per industry technical commentary, to the crystal growth itself — at growth temperatures above 2,000°C, scaling the diameter makes temperature uniformity, thermal stress, bow and warp, and defect suppression (micropipes, basal plane dislocations) all harder at once, and SiC is far more difficult to slice and polish than silicon.

Meanwhile, a new demand axis has appeared. With NVIDIA formalizing its 800VDC data center architecture roadmap (Aug 2026), data center demand for SiC power devices is opening up, and Wolfspeed reported its FY2026 AI data center revenue more than doubled year over year. Separately, there are reports of SiC interposers being adopted in NVIDIA's Rubin platform (TrendForce, Nov 2025) — but that is thermal and packaging demand, different in kind from power device demand.

What to check, then

Supplier financial health now matters as much as the spec

This downturn is actually removing substrate suppliers from the market. SK Siltron CSS bought DuPont's SiC wafer business for $450 million in 2019 and secured a $544 million US Department of Energy (DOE) loan in October 2024 — yet amid the EV slowdown and oversupply, after SK Siltron posted a consolidated net loss of KRW 293.6 billion for 2025 (mostly the SiC unit), the business entered liquidation in July 2026 (The Elec, Jul 2026). This was Infineon's 200mm multi-sourcing partner. In other words, qualification by a leading IDM is no guarantee a supplier survives. Wolfspeed filed for Chapter 11 in June 2025 and emerged that September with debt cut by about 70%, but earnings volatility remains even after restructuring — its quarterly guidance has come in well below market expectations (earnings coverage, Aug 2026).

For an item like wafers, where qualification takes time, a supplier disappearing turns the requalification period into a straight supply gap. Before signing a long-term supply agreement, checking financial statements, the parent's willingness to support the unit, and any divestiture talk is now as important as the spec discussion — as is writing business-discontinuation notice obligations and last-time-buy clauses into the contract.

Six-inch and eight-inch need different strategies

Six-inch calls for attention to the turn into a rebound phase. If your budget was set against the 2024–2025 floor prices, it needs adjusting for the supply-tightening and premium reports since July 2026. That said, the rebound rests on a single report so far, so we recommend re-verifying the magnitude with your own quotations. Raw material is moving the other way too — bulk SiC feedstock has actually been edging up on environmental enforcement and capacity constraints (TrendForce, Nov 2025).

Eight-inch has no standard market price, so the method of comparing quotes has to change. With no market baseline, the only option is to fix the specification — conductivity type (N-type/semi-insulating), thickness, TTV/bow/warp limits, micropipe density, and whether epi is included, all fixed in a single spec document, with quotes collected from multiple suppliers against that same document and compared relative to one another. For long-term volume, locking in a fixed price with no reopener clause is dangerous for both sides — eight-inch prices have a track record of falling to a third in little over a year. The AI data center demand discussed above is a variable pointing the other way — the more that demand axis materializes, the sooner both the six-inch rebound and the race to lock up eight-inch capacity could accelerate.

The procurement environment in Korea

Korea imports roughly 90–95% of its power semiconductors (digitimes-affiliated reporting). With the country's only dedicated substrate affiliate now in liquidation, the largest 200mm SiC production site in Korea belongs to a foreign company — onsemi's Bucheon fab. The government's roughly KRW 500 billion SiC development program is reported to have stalled at the planning stage for lack of an anchor demand company (digitimes, Aug 2026). If import dependence is the structure for the foreseeable future, then vetting and diversifying import sources becomes that much more important in practice. The customs and regulatory side is covered in our SiC import guide for Korea.

Frequently asked questions

Are eight-inch wafers more economical than six-inch right now?

Not yet. The roughly 20% per-die cost advantage over 150mm is a five-to-seven-year projection (Power Electronics News), and in the early transition there is no saving, due to substrate prices and process yield. Adopting eight-inch today is less about cost than about securing long-term capacity and aligning with supplier roadmaps.

When does the eight-inch transition become mainstream?

TrendForce (May 2025) puts the point at which eight-inch exceeds 20% of total shipments at 2030. Compared with earlier forecasts that expected 15% by 2026, that is a substantial delay. Yole expects the downturn to run through 2027–2028, with eight-inch driving the regrowth that follows.

Is six-inch about to disappear?

No. In July 2026, reports emerged that six-inch supply had actually tightened and prices had begun to rebound. Flip the forecast that eight-inch passes 20% in 2030, and it means the majority of shipments remain six-inch until then.

Where can I check the market price for eight-inch substrates?

There is no published standard price yet. The last public estimate was about $1,000 in Q1 2025 (TrendForce-affiliated reporting), and we could not confirm actual transaction prices since then from public sources. That is why relative comparison of multiple same-spec quotations, rather than checking against a market price, is the realistic way to verify.

References (public sources)

• TrendForce, May 2025 — 2024 global SiC N-type substrate revenue and supplier market shares.
• TrendForce, Nov 2025 — the six-inch substrate price war and rising bulk SiC feedstock prices.
• TrendForce, Mar 2025 — ST's China joint-venture eight-inch line coming online.
• TrendForce, Mar 2026 — Chinese suppliers unveiling 12-inch and 14-inch prototypes.
• Yole (via semiconductor-today), Dec 2025 — upstream and device utilization; downturn expected to last through 2027–2028.
• Wolfspeed, Sep 2025 — announcement of completed Chapter 11 financial restructuring.
• The Elec, Jul 2026 — SK Siltron CSS entering liquidation.
• US Department of Energy (DOE) LPO — SK Siltron CSS loan program.
• Infineon, Feb 2025 — first 200mm-based products shipped to customers.
• Bosch (via semiconductor-today), Jul 2026 — Roseville 200mm conversion and finalized CHIPS direct funding.
• onsemi, Oct 2023 — completion of the Bucheon fab expansion.
• Power Electronics News — die count and per-die cost analysis of the 150mm-to-200mm transition.
• digitimes, Oct 2024 — year-by-year statistics on China's SiC substrate capacity.
• digitimes, Aug 2026 — reporting on the stalled Korean SiC development program.
• STMicroelectronics — FY2025 Form 20-F annual report.

The figures and timelines above reflect public reporting as of the time of writing; eight-inch prices and individual ramp schedules in particular can change without public announcement.

Nami Tech Solutions (NTS) does not hold SiC wafers as standing inventory. We work project by project instead — fixing the specification in a single document, contacting manufacturers directly in their own language, and bringing back quotations on identical terms, side by side. On eight-inch, where no standard market price exists, that relative comparison is in practice the only way to verify a price.