Company history

In December 1954, fresh out of the science and engineering faculty of Ritsumeikan University, Sato Kenichiro started a one-man business in the Kamigyo ward of Kyoto under the name Toyo Denki Seisakusho. Its product was the carbon-film fixed resistor — the cheapest, most anonymous component in any electronic set. The brand he coined for it, ROHM, was simply resistance and the unit that measures it, and it eventually replaced the company name.

Incorporated in 1958 with ¥2 million of capital and a plant at Saiin in western Kyoto, the firm set out to do two things at once that rarely go together: hold quality first — the stated corporate purpose was to supply good products “continuously and in volume, at home and abroad, whatever the difficulty” — and control cost hard enough to make a commodity part profitable. From 1966 it began putting manufacturing subsidiaries into the provinces, starting with Wako Denki in Okayama, but on an unusual footing: rather than owning them outright, Rohm asked prefectural offices and chambers of commerce to introduce capable local managers who lacked an opportunity, then ran each plant as a joint venture with the man it had found.

Resistors gave the company a steady base and very little future. Sato’s attention was already moving to transistors and integrated circuits, and the question that would define the next twenty years was how a small passive-component maker in Kyoto could enter semiconductors at all without being crushed by the electrical giants.

Rohm entered integrated circuits in 1969, and did so by choosing not to compete. While Hitachi and Toshiba poured capital into commodity DRAM, Rohm aimed at custom ICs for video and audio equipment — and inside that, at audio rather than the television sets the majors cared about. Sato was candid that the niche had a low ceiling: custom work does not scale with headcount, and product lives are short. It was, nonetheless, ground he could hold.

The method reached its purest form in 1989, when Rohm entered the SRAM market by targeting the obsolescent 16K and 64K parts the majors had left behind as they moved up in density. Sato called it not a second-runner but a “third-runner strategy”, and cut development spending by buying circuit designs from American design houses — “about 80% cheaper than developing from a blank sheet,” as he put it. Cost accounting, not process leadership, was how Rohm made semiconductors pay. By 1983 it held third place in domestic resistors (13.8%), fifth in diodes and sixth in transistors, and it led outright in such quiet specialities as laser diodes for CD players and thermal printheads for fax machines.

Internationalisation came early and independence came with it. A US sales company was set up in Silicon Valley in 1970, only sixteen years after founding, a manufacturing subsidiary (Exar) followed in 1971, and the 1986 purchase of Exel Microelectronics added EEPROM capacity — and, amid the US–Japan semiconductor friction, supply that counted as American. Overseas sales settled at roughly 60% of the total and stayed there. At home the company renamed itself Rohm in 1981, listed on the Osaka exchange in 1983, moved to its first section in 1986 and reached the Tokyo Stock Exchange’s first section in 1989. Sato kept his distance from Kyoto’s business establishment and skipped even his own company’s induction ceremonies; Nintendo’s Yamauchi Hiroshi, one of the few peers he saw, wondered aloud whether he was “a great lone wolf or simply an eccentric.”

The bubble burst just as Rohm reached the first section, and the semiconductor slump that followed produced the most characteristic act of Sato’s career. Seeing operating margin fall to 2% in the interim results for 1990 — when depreciation was easing and profit should have been rising — he concluded the fault was inside: orders taken without regard to profitability, and an organisation that had grown comfortable. At the June 1991 general meeting he removed five directors, three of them managing directors. He then told all 260 salespeople to “go and cut the orders we don’t need,” and made set makers accept both price increases on components and a sharp reduction in the range they could order.

It worked, and in the worst possible market. For the year to March 1992 Rohm posted record sales of $1.5B (¥186bn) and ordinary profit of $110.5M (¥14bn) in the middle of a semiconductor recession; part numbers fell from 150,000 to under 100,000 and planned capex was cut by 40%. Sato’s justification was that a component maker earning only a fair return cannot reinvest, and that set makers would suffer for it — coupled with a flat refusal ever to move downstream: “we remain a component maker; we do not make sets.”

The two decades that followed were the payoff. Custom ICs for consumer equipment carried sales past ¥300bn by March 2000 and to ¥387.8bn by March 2006, with a 17.6% operating margin, an equity ratio above 80% and no interest-bearing debt at all — a profile no other Japanese chipmaker held while the industry around it went through crisis after crisis. But the model was reaching its limit. In October 2008 Rohm made the first acquisition in its history, buying Oki Electric’s semiconductor business to widen an LSI line-up it could no longer extend on its own, and in June 2009 Sato stood down after fifty-four years, handing the presidency to a career employee, Sawamura Satoshi. Owner rule ended and committee rule began.

The pivot began within weeks of the succession. In July 2009 Rohm bought SiCrystal of Germany to bring silicon-carbide wafers in-house — a material only a handful of firms in the world could make — and then moved down the chain: SiC Schottky barrier diodes in 2010, and in January 2012 the first volume-produced SiC MOSFET in the world, ahead of the integrated electrical giants that had hesitated to commit. For the first time Rohm was not picking up ground the majors had left; it was arriving before them.

The cost of the transition showed immediately. The year to March 2012 brought the first net loss in the company’s history, ¥16.1bn, and the next year an operating loss with sales down to ¥292.4bn. Recovery came from doing what Rohm had always done — clearing unprofitable LSI lines and concentrating on power devices and analog ICs — and sales were back above ¥350bn by March 2014. Presidents changed quickly (Fujiwara Tadanobu in 2017, Matsumoto Isao in 2019, who introduced a CEO structure), but the direction did not; by March 2019 the company was earning a 14.0% operating margin on sales of ¥399.0bn.

The target market shifted with it. The December 2019 purchase of part of Panasonic’s semiconductor device business brought automotive power products and, more valuably, direct relationships with carmakers. In 2021 the medium-term plan MOVING FORWARD to 2025 made automotive and overseas growth explicit, and the EV boom did the rest: the year to March 2023 set records at $3.6B (¥508bn) in sales and ¥92.3bn in operating profit, an 18.2% margin. Rohm then committed ¥510bn of investment over seven years, with SiC taking roughly 70% of group capex and annual spending passing ¥100bn — the largest wager in its history, made by a company whose entire method had been to avoid making wagers of that kind.

In 2023 Rohm committed $2.1B (¥300bn) to the consortium taking Toshiba private — one of the largest single contributions in that deal — in order to build a footing for cooperation in power semiconductors that capital spending alone could not buy. It was also the end of the company’s defining financial trait: the equity accumulated by seventy years of caution was spent, and the debt-free balance sheet went with it.

Within two years the premise had turned. EV demand slowed, Chinese suppliers moved faster than expected, and the Toshiba relationship settled into mutual production rather than the synergy that had been hoped for. Impairments on SiC-related assets pushed Rohm to its first net loss in twelve years in the year to March 2025. In 2026 the company received an acquisition proposal from Denso, Japan’s largest automotive supplier, reported at up to $8.2B (¥1.3tn) — an outcome that would end the independence Sato Kenichiro treated as the point of the whole enterprise.