Samsung Electronics and SK Hynix have both secured production-ready technology for 16-layer stacks of sixth-generation high-bandwidth memory, known as HBM4, positioning the two South Korean memory makers for a pivotal contest in 2026 as demand from artificial intelligence accelerators expands. While each company has demonstrated technical readiness, industry participants say yield performance, rather than headline specifications, is likely to determine market share, profitability, and supplier standing in the next phase of the HBM cycle.