Company history

Kioxia’s line runs back into the semiconductor business of Tokyo Shibaura Electric — Toshiba. The company prototyped a transistor at its Komukai works in Kawasaki in January 1951, early even by Japanese standards, and by 1956 was one of the first Japanese firms licensed to use Bell Labs and Western Electric transistor technology, alongside Tokyo Tsushin Kogyo (later Sony) and Hitachi. In the DRAM race of the 1980s Toshiba chose the planar cell and low-power CMOS over the harder-to-build three-dimensional structures its rivals pursued, and won on sheer manufacturability: at the 1-megabit generation it more than halved power consumption, lifted yields, and by 1986 was building a million parts a month — the world leader in that product category. The same year Japan overtook the United States in overall semiconductor share, which brought the retaliation of the US–Japan Semiconductor Agreement of September 1986.

The product Kioxia lives on today was invented in those labs. From around 1980 Masuoka Fujio led non-volatile memory work at the Kawasaki research centre, presenting a single-transistor flash cell — later called NOR — at the IEDM conference in 1984, and at IEDM 1987 the world’s first NAND flash memory, whose cells were wired together to raise storage density per unit of area. A colleague, Ariizumi Shoji, is credited with naming it “flash,” because erasing a whole block at once was as quick as a camera flash. Both the technology and the name came out of Toshiba.

Toshiba shipped the world’s first 4-megabit NAND product in 1991 and built the Yokkaichi plant in Mie prefecture in 1992 as its manufacturing base. In that same year it licensed NAND to Samsung Electronics, which used the licence as a foothold, invested at a scale Toshiba would not match, and became the largest memory maker in the world. The inventor left too: dissatisfied with how he had been treated, Masuoka moved to Tohoku University in 1994 and later sued Toshiba over compensation for the invention, settling in 2006. Invention and commercialisation parted company early here — a pattern that would repeat.

In 2000 Toshiba began working with SanDisk of the United States on flash memory and set up a 50/50 joint venture aimed at production in Yokkaichi. In December 2001 it walked out of commodity DRAM altogether, selling its Virginia fab to Micron Technology. Giving up the business that was fought over on price and concentrating resources on the memory it had itself invented left Toshiba’s memory operation built around NAND and its applications, with Yokkaichi as the core site — a division inside a diversified electrical conglomerate, but one running on an investment cycle of its own.

Yokkaichi expanded through the SanDisk partnership. Toshiba owned and operated the plant while the two firms split the capital spending and the wafer output down the middle, adding fab buildings through a succession of joint ventures — Flash Partners, Flash Alliance, Flash Forward. New 300mm buildings came up one after another, and each generation of shrink lowered the cost per bit. Against Samsung and SK Hynix in a permanent race of miniaturisation and capacity, the Toshiba–SanDisk pairing held its place among the leading suppliers of NAND in the world.

When shrinking approached its physical limit, Toshiba went vertical. It developed three-dimensional flash in 2007, later naming it BiCS FLASH, and began sampling a 48-layer part in 2015. In 2011 memory and SSDs were gathered into a dedicated in-house company, and as smartphones and data centres spread, memory grew into the single largest source of profit inside Toshiba — a business standing beside nuclear power and infrastructure, but with capital requirements and cyclical swings unlike anything else in the group. In May 2016 SanDisk was bought by Western Digital, so the Yokkaichi partner became a hard-disk company. The ever-heavier cost of each new NAND generation is what would soon decide the fate of the business, once Toshiba itself ran into trouble.

What pulled the memory business out of Toshiba’s hands was a crisis at the parent. In 2015 an independent committee found that Toshiba had overstated operating profit by roughly $1.3B (¥152bn) since fiscal 2008, and president Tanaka Hisao and other directors resigned. Then came the American nuclear subsidiary Westinghouse: construction cost overruns forced enormous goodwill impairments, and on 29 March 2017 Westinghouse filed for Chapter 11 bankruptcy. Toshiba faced negative net worth and, if that ran two years in a row, delisting. The most valuable thing it could sell was the memory business that was still growing. In February 2017 it set up Toshiba Memory Corporation as the receiving vehicle and on 1 April transferred the memory and SSD business into it by company split — a fast route out of negative equity, and a way to detach a capital-hungry business from the parent’s credit.

The auction drew Broadcom’s consortium, Hon Hai, SK Hynix and Western Digital, and bids climbed past ¥2tn. In June 2017 Toshiba chose a Japan–US–Korea consortium — the INCJ, the Development Bank of Japan, Bain Capital and SK Hynix — and in September signed with Bain’s acquisition vehicle, Pangea. Western Digital, the joint-venture partner, went to international arbitration arguing that its consent was required before Toshiba could move its interest to a third party, and sought to block the sale; that dispute was settled in December on terms extending and strengthening the joint venture. After Chinese antitrust clearance, the sale closed on 1 June 2018 at about ¥2tn — among the largest business sales Japan had seen. Pangea’s voting rights were split Bain 49.9%, a reinvesting Toshiba 40.2% and the optics maker HOYA 9.9%, so Japanese holders together held a majority; SK Hynix came in through convertible bonds, and Apple and Dell put money in without votes. Technology and production stayed in Japan; the logic of the capital was a foreign fund’s.

Under Bain, the company built itself a holding structure and a new name. In March 2019 a share transfer created Toshiba Memory Holdings above the operating company, and that October the whole group was renamed Kioxia — a coinage from the Japanese 記憶 (kioku, memory) and the Greek axia, value, picked from an employee competition. Dropping the Toshiba name declared independence from the old parent and an intent to compete worldwide as a pure-play memory maker. But independence meant funding the continuing multi-hundred-billion-yen investment at Yokkaichi and Kitakami on its own credit rather than Toshiba’s: in June 2019 it raised preferred shares taken up by the Development Bank of Japan and a syndicated bank loan. To carry generational investment on that scale through the swings of the memory cycle, it would need a thicker capital base — which made a stock-market listing the obvious next objective.

Kioxia aimed at a listing almost as soon as it was independent, and twice stood down. In September 2020 it postponed a planned Tokyo listing, citing US–China tensions, the American export controls aimed at Huawei — a major customer — and a market softening under COVID. In parallel a combination with Western Digital was explored: a share-exchange proposal surfaced in 2021 and talks revived in 2023 around a new company headquartered in Japan. The two ran Yokkaichi and Kitakami on a fifty-fifty basis already; merged, they would have been a NAND maker on a scale approaching Samsung’s.

The talks collapsed in October 2023, and the reason was that a shareholder, SK Hynix, would not agree. Having joined the 2018 consortium through convertible bonds, SK Hynix held a large interest in Kioxia’s value and objected that a merger with a competitor would damage its own investment; terms with Bain, which had assembled Pangea, could not be bridged either. The plan to unite the two firms that had shared the lineage of the invention was defeated by a complicated coalition of capital. Western Digital afterwards turned instead to separating its own flash business as SanDisk.

Kioxia listed on the Tokyo Stock Exchange Prime Market on 18 December 2024 at an offer price of ¥1,455, closing its first day at ¥1,601 — four years after the first attempt, and directly after the worst of the cycle: in the year to March 2024 revenue was $7.1B (¥1.08tn) with an operating loss of $1.7B (¥253bn) and a net loss of $1.6B (¥244bn). Then demand from generative AI and data-centre SSDs turned it around — $11.4B (¥1.71tn) of revenue and $1.8B (¥272bn) of net profit in FY2025, and records across the board in FY2026 at $14.8B (¥2.34tn) of revenue, $5.5B (¥870bn) of operating profit and $3.5B (¥555bn) of net profit. That a loss and a record can trade places within two years is the other face of a business that makes one product.

The listing also rewrote the register. Bain sold down in stages and let go of its last holding in July 2026, exiting completely after eight years; Toshiba cut its stake too, to 17.59% at March 2026, but in a now-dispersed register that left the old parent as the effective largest shareholder — a fitting shape for this company’s history. Through the whole fund era, management stayed in the hands of Toshiba-trained engineers: the first president Naruke Yasuo, Hayasaka Nobuo who ran the company from 2020 to 2026 and took it public, and Ota Hiroo, who succeeded him in 2026. Ownership moved from a foreign fund to the market, but the technology Toshiba created, and the people carrying it, held the business together.