South Korea's KOSPI Composite Index closed up 2.8% at 2,948 on Thursday — the highest level since the 2024 peak — as semiconductor heavyweights drove a $34 billion single-session gain in aggregate market capitalization. Samsung Electronics (005930.KS) rose 6.4% to ₩88,400, while SK Hynix (000660.KS) surged 9.2% to ₩262,500. The won closed at 1,378.40 against the U.S. dollar, broadly stable on the session despite USDKRW reaching 1,381 intraday.
The catalyst was confirmation from supply-chain sources that both Samsung and SK Hynix have completed qualification of their HBM4 12-high stack memory product at all four major U.S. hyperscalers — Microsoft, Amazon Web Services, Google Cloud and Meta — on Nvidia's upcoming Vera Rubin platform. SK Hynix CFO Kim Woo-hyun confirmed in a Q1 post-earnings call Thursday morning that "HBM4 commercial shipments are now planned for July, three months ahead of our prior schedule."
HBM Pricing Power
TrendForce data Thursday showed HBM4 12-high price premium versus HBM3E 12-high is currently 47%, well above the 30% premium that had been the consensus assumption for the cycle. Total HBM bit demand for the second half of 2026 is now estimated at 84 billion gigabits, up from the prior 62 billion estimate. Samsung's memory operating margin is forecast to expand to 38% in Q3 (from 28% in Q1) per Nomura analyst Jiyon Cho.
Korean memory ADRs rallied in U.S. trade: SK Hynix ADRs (HXSCL) up 9.4%, Samsung ADRs up 6.0%, with the iShares MSCI South Korea ETF (EWY) closing up 4.2% — the steepest single-session gain since November 2024. Local supply-chain peers also gained: Hanmi Semiconductor (042700.KQ) +12.4% (TC bonder), HPSP (403870.KQ) +8.6% (high-pressure annealing), Wonik IPS (240810.KQ) +6.4% (deposition equipment).
Currency and Monetary Policy
The won's relative stability — down only 0.4% on the session despite broad U.S. dollar strength — reflected the offsetting effect of strong export-related capital inflows. Bank of Korea Governor Rhee Chang-yong told reporters at the World Economic Forum side panel Wednesday that the central bank will "not be in a rush to follow Fed pricing" and reiterated the 2.75% terminal rate guidance through Q3. Three-year KTB yields fell 4 bps to 2.81%.