The KOSPI dropped 10.84% and triggered a circuit breaker as a regional chip selloff hit Korean memory stocks. Analysts differed over CXMT's near-term supply impact.
Chinese memory-chip maker CXMT closed its July 27, 2026, Shanghai debut at 49 yuan, 465.82% above its 8.66 yuan offer price. The following day, as concerns about competition from Chinese suppliers intensified, Samsung Electronics fell 13.39% and SK hynix dropped 14.65% in the regular session in Seoul. The KOSPI sank 10.84%, prompting a 20-minute marketwide trading halt.
Reuters reported that CXMT's listing added to concerns about stronger competition in the global memory industry. The selloff also reflected doubts about AI infrastructure financing, elevated semiconductor valuations, reports about Chinese chipmaking equipment and caution ahead of major technology-company earnings.
Samsung and SK hynix posted double-digit declines
Samsung Electronics closed down 34,000 won at 220,000 won on July 28. SK hynix fell 266,000 won to finish at 1.55 million won.
| Stock or index | July 28 close | Regular-session move |
|---|---|---|
| Samsung Electronics | 220,000 won | -13.39% |
| SK hynix | 1.55 million won | -14.65% |
| KOSPI | 6,023.66 | -10.84% |
| Kosdaq | 705.85 | -7.72% |
The KOSPI lost 732.09 points to close at 6,023.66. At 10:14 a.m. local time, a decline of more than 8% triggered a circuit breaker that halted trading in KOSPI-listed shares for 20 minutes. Foreign investors sold a net 4.97 trillion won of shares on the main market.
Before the Seoul market opened, SK hynix's U.S.-listed depositary receipts had closed 7.5% lower at $143.02 in the July 27 U.S. regular session. It was their first close below the $149 offer price set for the U.S. listing earlier in July. The PHLX Semiconductor Index fell 2.2% in the same session.
CXMT's debut added to China competition concerns
CXMT began trading on the Shanghai Stock Exchange's STAR Market on July 27. The shares closed at 49 yuan, 465.82% above the 8.66 yuan offer price, giving the company a closing market capitalization of about 3.28 trillion yuan.
Reuters reported that the debut reinforced concerns about CXMT expanding production capacity and adding supply to the global memory market. Ryu Young-ho, an analyst at NH Investment & Securities, told Reuters that perceptions of CXMT becoming a more formidable supplier increased concerns about oversupply and weaker pricing.
CXMT is China's largest and the world's fourth-largest DRAM producer. According to Counterpoint Research figures cited by the Associated Press, Samsung accounted for 36% of global DRAM shipments in 2025, SK hynix for 29%, Micron for 24% and CXMT for about 8%. CXMT's share reached approximately 9% in the first quarter of 2026.
DUV equipment reports and AI financing also weighed
Market participants cited by Reuters did not attribute the July 28 selloff to CXMT alone. Reports that Chinese companies were developing domestic deep ultraviolet lithography equipment also revived concerns that Chinese memory manufacturers could expand capacity.
Han Ji-young, an analyst at Kiwoom Securities, told Reuters that the companies involved, equipment performance and commercialization schedules had not been disclosed. He said the reports nevertheless added pressure to semiconductor sentiment that had already weakened.
Concerns about AI infrastructure spending were also present. Nvidia shares fell nearly 5% in the July 27 U.S. regular session after The Wall Street Journal reported that the company could provide roughly $250 billion in financial support for an OpenAI data-center project. Reuters reported that investors questioned the extent to which an AI-chip supplier might be financing its customers' infrastructure.
Analysts differed on CXMT's near-term supply impact
A separate assessment said CXMT was unlikely to change global DRAM supply materially in the near term. In a July 28 report, Eugene Investment & Securities analyst Son In-joon said it was premature to treat CXMT's listing and Shanghai fab expansion as a signal of near-term global DRAM oversupply.
Eugene Investment & Securities distinguished between nominal wafer capacity and effective bit output. The firm said CXMT uses multipatterning without access to extreme ultraviolet lithography and estimated that uncertainty around stable 1a-class production and yields leaves it two to three process generations behind Samsung and SK hynix.
In its second Shanghai session on July 28, CXMT closed 4.08% lower at 47 yuan. Its market capitalization at the close was about 3.14 trillion yuan.