Toshiba, Rohm and Mitsubishi Electric Join Forces: Inside Japan's Bid to Build the World's No. 2 Power Semiconductor Maker

Power semiconductors are the valves of the electric world: they directly determine an EV's driving range, how fast a charger charges, and the power efficiency of AI data centers (article in Japanese). As the industry shifts generations from silicon to new materials — SiC (silicon carbide) and GaN (gallium nitride) — Japan's three big players were pushed toward consolidation by the sheer weight of the required investment and a structural change in competition.

What is a power semiconductor, and why does it matter in the EV era?

A transistor is an electric switch, and a power semiconductor is the specialized version built to handle large currents and high voltages. The inverter that drives an EV's motor, the voltage conversion inside a fast charger, industrial motors in factories, railway traction systems, and the backup power and supply circuits of data centers — wherever electricity is converted, a power semiconductor is doing the work.

The global power semiconductor market was worth about 52.5 billion dollars in 2024 and is projected to grow to about 81.7 billion dollars by 2034. The growth engine is SiC for EVs, forecast to expand to about 10.3 billion dollars by 2030 at roughly 20% a year. Because SiC cuts switching losses dramatically compared with silicon, the same battery delivers longer EV range and chargers can shrink. As we noted in our overview of the EV and battery industry (in Japanese), EV adoption is structurally generating demand for power semiconductors centered on SiC.

Why does Infineon lead, and why were Japan's players fragmented?

In 2024 power semiconductor market share, Infineon held about 17.4%, the world's top position. The gap to the rest is wide, and the top five in SiC device revenue — STMicroelectronics, onsemi, Infineon, Wolfspeed and Rohm — control about 91.9% of it. Behind this oligopoly lies a gap in vertical integration.

Infineon has been internalizing SiC wafer production at its Dresden site, letting one company control cost and quality from raw material to finished product. Japan's players, by contrast, each specialized in their own strengths while cooperating loosely — but staying independent and spreading investment thin raises the risk that the sheer cost of the SiC transition crushes each company's finances individually.

Wolfspeed's bankruptcy: what did it prove about the weight of SiC investment?

Wolfspeed held about 33.7% of the world SiC substrate market and was the first to run a 200mm wafer mass-production line — and in 2025 it filed for Chapter 11 restructuring under about 4.6 billion dollars of debt. The cause was the gap between massive fab investment and the delayed ramp of EV demand. Wolfspeed's collapse confronted the entire industry with a hard truth: SiC is harder to manufacture than silicon and takes years to reach healthy fab utilization — so a standalone player without scale runs out of money first.

What does each of Rohm, Mitsubishi Electric and Toshiba bring?

Rohm is the pioneer that mass-produced the world's first SiC MOSFET — the SiC switching device — in 2010. By acquiring Germany's SiCrystal, a SiC wafer maker, it achieved vertical integration from substrates to semiconductor devices. Owning the upstream material stabilizes costs while keeping technology development under one roof. In December 2023, a division-of-labor partnership with Toshiba — Rohm on SiC, Toshiba on silicon — was certified by Japan's Ministry of Economy, Trade and Industry, winning a 388.3 billion yen project with up to 129.4 billion yen in subsidies.

Mitsubishi Electric is No. 2 worldwide in power modules — packaged units integrating IGBTs and other devices (per Omdia) — and holds the top global share in power modules for VSC-type HVDC (high-voltage direct current transmission). Its overwhelming track record in railways, industry and renewable energy, and its systems-level energy expertise, are its edge. In 2026 it brought a new 8-inch SiC production line online in Kumamoto, moving its SiC transition into full gear.

Toshiba, after spinning off its NAND flash business (now Kioxia) in 2018, concentrated its resources on power devices and discrete semiconductors — single-function individual chips. It completed a 300mm-capable fab building at its Kaga plant in 2024, lifting production capacity for low-voltage MOSFETs and IGBTs — both power-switching devices — to 2.5 times the fiscal 2021 level. Toshiba's strength lies not in SiC but in stable IGBT volume production and its lineup of automotive and industrial discretes.

Why did the three companies decide to combine in March 2026?

In March 2026, Toshiba, Rohm and Mitsubishi Electric announced a basic agreement to begin merger talks for their power semiconductor businesses. Their combined global share is roughly 10% — second in scale only to Infineon.

Three structural forces sit behind the deal. First, the scale of investment: a full transition to SiC requires capital spending in the hundreds of billions of yen, from wafer lines through device fabrication and evaluation, and is becoming hard for any single company to sustain. Second, the Chinese catch-up: as in mature silicon nodes, domestic Chinese makers are rapidly expanding SiC capacity, building medium-to-long-term price pressure. Third, demand is arriving in earnest: the judgment is that EV-driven SiC demand will enter its acceleration phase after the 2025-2026 adjustment period. A merger concentrates R&D spending and creates an end-to-end manufacturing structure combining Rohm (SiC materials), Mitsubishi Electric (modules and systems) and Toshiba (IGBTs and automotive discretes).

Where can the Japanese alliance stand in SiC market share?

In SiC devices, STMicroelectronics led with 32.6% in 2023, and the top five control about 91.9%. Rohm sits among those top five.

Even once the Japanese alliance forms, there is no guarantee it immediately overtakes ST or Infineon in SiC. The next questions are how it uses the hole Wolfspeed left in US SiC production capacity, and how it builds supply relationships with the EV makers — European, American and Chinese — at the center of demand. At the same time, the merger of three companies that spent decades building up the fundamentals of power semiconductor technology (article in Japanese) marks a historic turning point: Japan's semiconductor industry is committing in earnest to the new market where EVs meet power infrastructure.

Key takeaways

• The power semiconductor market is headed for about 81.7 billion dollars by 2034, driven by EVs, fast charging and data center power.
• Infineon leads overall with about 17.4%. In SiC devices, STMicroelectronics leads with 32.6%, and the top five hold about 90%.
• Rohm: world's first SiC mass production (2010) and vertical integration via SiCrystal. Mitsubishi Electric: No. 2 in power modules, No. 1 in HVDC. Toshiba: 2.5x capacity at its Kaga 300mm fab.
• Wolfspeed's bankruptcy showed the industry that SiC cannot be fought without scale.
• The three-way basic agreement of March 2026 aims to create a Japan-born, world No. 2-scale power semiconductor alliance.