Micron Breaks Ground on 1.5 Trillion Yen Hiroshima Fab, Japan's Only DRAM Site Targets HBM4

While the world watches TSMC, a groundbreaking in Hiroshima deserves equal attention. Micron is investing 1.5 trillion yen — roughly 1.5 times TSMC's first Kumamoto fab — in a new building at its Hiroshima plant, where a new cleanroom will develop and mass-produce HBM4, the next-generation high-bandwidth memory that feeds AI accelerators. The site is Japan's only remaining DRAM fab, built on the grave of Elpida, whose 2012 bankruptcy ended Japan's homegrown DRAM industry before Micron acquired it in 2013. Only three companies in the world can mass-produce HBM, and Micron is betting its most valuable product line on Japan, backed by repeated METI subsidies that place Hiroshima alongside TSMC Kumamoto and Rapidus as pillars of Japan's chip revival. The scenarios split on the AI capex cycle: on-schedule HBM4 ramp captures the next AI server generation; a memory downturn would stretch payback painfully, as memory cycles always do. Watch HBM4 yield news, future subsidy terms, and — following the Kumamoto playbook — land prices around Higashihiroshima, because fab towns have become Japan's most durable real-estate story. The ticket to Japan's DRAM comeback costs 1.5 trillion yen; the open question is whether AI demand keeps paying for it.