Memory Shift to HBM4: Micron Halted from DRAM Leadership, SK and Samsung Expected to Gain Share

HBM4 entering verification and production is shifting memory demand back to SK Hynix and Samsung, while Micron (MU) faces significant share erosion. NVIDIA's Vera Rubin and AMD's Instinct MI400 architectures accelerating HBM4 adoption have pressured Micron's HBM4 qualification, with sources citing validation bottlenecks in packaging, pin speed, and process precision. Micron is re-engineering its base chip and power distribution/PHY architecture to meet HBM4 by Q2 2026, but by then, SK Hynix is expected to capture over 50% of the HBM4 market and Samsung 20%–30%, depending on Micron's progress. Micron's vertical integration strategy and focus on cost and supply chain control may preserve strength in general-purpose DRAM, particularly with SOC AMM transitions.