Micron broke ground on a $9.3 billion Hiroshima expansion built for one purpose: making the high bandwidth memory that keeps Nvidia's AI chips running, and challenging SK Hynix's grip on that market.
On Saturday, in Higashi-Hiroshima, Micron turned the first soil on a 1.5 trillion yen expansion of its existing plant there, according to Bloomberg. The company plans to use the new capacity to build high bandwidth memory, the stacked chips that sit next to processors like Nvidia's and feed them data fast enough to keep up with AI workloads. Shipments are expected to start around the summer of 2028.
You don't build a plant this size on a hunch. Micron and Samsung are still chasing SK Hynix in HBM, and Micron is spending nearly $10 billion to close that gap. Japan's Ministry of Economy, Trade and Industry is subsidizing the project too, kicking in up to 500 billion yen, or roughly $3.2 billion, according to Bloomberg. That's not charity. Tokyo has spent years trying to rebuild a domestic chip industry it let slip to Taiwan and South Korea in the 1990s, and HBM is the one segment where a Japanese win is still plausible.
SK Hynix isn't standing still. The company held around 58 percent of the global HBM market in the first quarter of 2026, with Samsung and Micron splitting most of the rest near 21 percent apiece, according to data compiled by TrendForce. Reuters recently reported that SK Hynix has overtaken Samsung as South Korea's most valuable listed company, a turn built almost entirely on HBM demand from Nvidia and other AI chip buyers. Micron's Hiroshima bet is the clearest sign yet that it isn't content to stay in third place.
Micron already runs a DRAM fab in Higashi-Hiroshima, acquired when it bought Elpida Memory out of bankruptcy back in 2013. Building HBM capacity there instead of at a greenfield site cuts years off the timeline and gives Micron another geography outside Taiwan, where the bulk of the world's advanced chip packaging still happens. A single earthquake, a single flashpoint near the Taiwan Strait, and a huge share of the AI industry's memory supply is exposed. Spreading HBM production across Japan, Korea and the United States isn't a nice to have anymore. It's how a supplier survives a bad year.
Micron CEO Sanjay Mehrotra has been blunt about what HBM actually is. He has called it a technical marvel, not your grandfather's memory, and noted that it takes far more wafers to produce than standard DRAM for the same output. That's the real bottleneck behind the AI chip shortage everyone keeps reading about. Fabs can't just spin up more HBM overnight. Building the equipment, qualifying the process and getting yields high enough to ship in volume takes years, which is exactly why Micron started digging in Hiroshima now for chips it won't sell from that site until 2028.
Nvidia's Vera Rubin platform has already pulled the next phase of the memory fight forward. Micron said at GTC 2026 that it had entered high volume production of 36GB 12-high HBM4 for Vera Rubin, while Reuters has reported that Samsung, SK Hynix and Micron have all passed Nvidia's HBM4 certification. The race hasn't ended, but it has changed shape. The question now is less who can prove the technology works, and more who can make enough of it at yields and prices that Nvidia, AMD and the cloud giants can actually build around.
Frankly, the subsidy math says as much about Tokyo's ambitions as it does about Micron's. Chip manufacturing is a business where the winner is often whoever can borrow money most cheaply and wait longest for a return. Japan is willing to eat roughly a third of Micron's bill because a functioning HBM supply chain on its own soil is worth more than the subsidy check. The same logic explains why the US CHIPS Act, South Korea's K Chips Act and now this Japanese package keep showing up wherever advanced memory or logic gets built. State money has become a normal input cost in this industry.
For the companies buying HBM, the practical upshot is capacity they can plan around. Nvidia, AMD and the hyperscalers building their own AI accelerators have spent the past two years absorbing every HBM chip SK Hynix, Samsung and Micron can produce, and prices have climbed accordingly. Micron's Hiroshima lines won't fix the shortage this year or next. But they give chipmakers another credible source of future volume, and that matters when one supplier has been able to set much of the pace.
Micron hasn't disclosed monthly output targets for the new lines, only that production will scale through the back half of the decade. Whether that's enough to meaningfully dent SK Hynix's lead by 2030 is still an open question. What's not in question is that Micron just committed nearly a decade of capital and Tokyo's money to finding out.
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