Chip Stocks Slump as Samsung and SK Hynix Lead Kospi Rout

Korean chip stocks fell sharply on Thursday, October 15, and the Kospi index closed down 7.57% at 5,554.22, according to the Korea Herald. The Kosdaq closed down 7.65%. SK hynix dropped 11.06% to 1.26 million won, and Samsung Electronics fell 9.48% to 210,000 won. Both markets triggered circuit breakers on the same day, the first time that had happened since July 29.

How the selloff unfolded.

The slide had started earlier in the week. On Tuesday, Samsung fell 7.39% and SK hynix fell 10.09%, the Korea Times reported. On Thursday the Kospi opened 5.59% lower and at one point fell more than 9% before recovering part of the loss. A sell-sidecar halted index futures-linked program trading at 9:07 a.m., and a market-wide circuit breaker froze trading for 20 minutes at 12:38 p.m. Foreign investors sold shares worth 3.62 trillion won, about $2.68 billion, while individuals and institutions were net buyers, the Korea Herald reports.

What is driving the move.

The reporting does not point to one confirmed trigger. Startup Fortune links the slide to rate worries, saying a hotter-than-expected US inflation reading on October 14 reduced bets on near-term Federal Reserve rate cuts. That hit companies that borrowed heavily for AI infrastructure, it reports, and CoreWeave's bond yields had already moved toward 15% earlier that week. The Korea Herald gives a related reason: US consumer prices rose 0.6% in September from August, the fastest monthly rise since April. Kim Seok-hwan of Mirae Asset Securities told the paper that volatility “is expected to persist in the near term.”

The CXMT 4F² DRAM factor.

Chinese memory maker ChangXin Memory Technologies, known as CXMT, has also entered the picture. TechNode, citing Yicai, reports that CXMT president Cao Kanyu outlined a plan on October 10 to launch a new generation of server DDR5 memory modules by the end of 2026, built on a 4F² cell architecture. The Korea Times says the design could theoretically cut cell area by 33% compared with the current 6F² standard. Startup Fortune puts CXMT's share of global DRAM below 10%, against roughly 39% for Samsung and 25% for SK hynix, and notes that industry estimates place Samsung's own comparable roadmap around 2028.

Why the plan does not settle the question.

Announcing a product is not the same as shipping it. The Korea Times quotes one industry official saying yields, customer buy-in and qualification are the key factors. A second official suggested the announcement was aimed at investors after CXMT's recent IPO, and said he had not heard of major server orders. TechNode notes that CXMT has published no performance figures and has not named customers. The Korea Times adds that CXMT's process is around 16 nanometres and that US-led export limits restrict its access to EUV lithography equipment, which makes the size gain uncertain.

What is still unknown.

The reporting does not establish whether this week's move marks a turn in the memory cycle or a short reaction to rates and rival announcements. Neither the Korea Herald nor Startup Fortune presents a confirmed cause, and the explanations overlap. Investors in other time zones who want to track when Seoul trading opens and closes can convert those hours with the free time zone converter at /en/time-zone-converter.