KOSPI Plunges 5% as China's CXMT Threatens Samsung and SK Hynix with Denser Memory Chips

South Korea’s KOSPI index fell nearly 5% to 6,100 on Tuesday morning as Chinese chipmaking advances spooked investors. The slide extends a five-day drop of over 10%, driven largely by ChangXin Memory Technologies (CXMT) reporting progress on a new 4F² chip design. Samsung Electronics and SK Hynix, which together account for more than half of the KOSPI's market value, both saw their shares fall roughly 5% in Seoul trading. TrendForce estimates the new architecture could increase memory density by 30% to 50%, with CXMT aiming to ship server memory built on the design by the end of the year. Foreign investors sold a net 341.4 billion won of shares during the Tuesday morning session, mirroring overnight drops from US competitors like Micron and SanDisk.