TSMC Kumamoto Fab 2 to Upgrade to 4 nm Process

According to a recent report from Nikkei, TSMC is evaluating an upgrade to the process technologies planned for its second-phase Kumamoto fab (Fab 23 Phase 2) in Japan, potentially shifting from the originally announced N6/N7 nodes to more advanced N4 (4 nm) and N5 (5 nm) production.

The report notes that it is not unusual for a foundry to enhance a fab’s roadmap as market demand evolves. Fab 23 Phase 2, located near Kumamoto and backed by an investment of roughly USD 13.9 billion, began construction in October 2024 and is scheduled to start operations by the end of 2027. The original plan targeted N6 and N7 production for applications such as autonomous driving and artificial intelligence.

If the upgrade proceeds as reported, the fab would add N4 and N5 capability, allowing TSMC to manufacture more advanced chips for Japanese customers. Although N5/N4 and N7/N6 are based on different design rules—with the former using up to 14 EUV layers—the production equipment overlaps significantly. Up to 90% of the tools used for N7/N6 can be reused for N5/N4, making the upgrade relatively straightforward. However, layout adjustments may still be required because N4 production relies on a larger number of EUV scanners, which occupy more space than DUV tools.

Nikkei also highlights that TSCM had already explored the possibility of N4 production in Kumamoto as early as 2023, suggesting the fab may have been scoped from the beginning to accommodate additional EUV capacity.

One unusual development is the recent slowdown at the construction site. Although heavy machinery such as cranes, excavators, and piling machines were active in late October, images taken in early December show that most equipment has been withdrawn. Several suppliers have reportedly been told that work is paused, without explanation.

Additional reports claim that TSMC informed equipment partners that no new tools will be required in Japan for all of 2026. This implies that, due to construction delays, installation at Fab 23 Phase 2 is unlikely to begin next year.