SK Hynix, Samsung Shares Slide, Dragging Kospi Nearly 8% Lower

By Kwanwoo Jun

Shares of Samsung Electronics and SK Hynix, the world's two largest memory-chip makers that together account for more than half of South Korea's Kospi, slumped on Thursday, dragging the benchmark index sharply lower and prompting regulators to halt trading to calm the market.

The Kospi ended 7.9% lower at 7648.09, slipping back below 8000 after briefly climbing above 9000 for the first time weeks earlier.

The sharp reversal was driven largely by the index's two heavyweight chip companies. SK Hynix and Samsung Electronics tumbled 15.0% and 9.1%, respectively.

Both stocks, beneficiaries of the artificial-intelligence boom and red-hot demand for advanced chips, retreated after U.S. technology shares fell overnight on Wall Street amid concerns about the sustainability of AI spending, as a report that Meta plans to launch a cloud business selling excess computing power to external customers also weighed on sentiment.

The Korea Exchange activated trading curbs for both the Kospi and the smaller tech-heavy Kosdaq markets after their futures fell more than 5% and 6%, respectively.

Zavier Wong, market analyst at eToro, noted that three trading halts by South Korean regulators in less than three weeks were all triggered by the same two stocks.

"Samsung and SK Hynix now make up around half the Kospi's total weight, up from around just a quarter at the end of last year," Wong wrote. "A sharp move in either name drags the whole index with it before the other roughly nine hundred listed companies get a say."

The retreat came as both companies began providing details of their massive investment plans to deepen South Korea's role in the AI supply chain. SK Hynix said Thursday that it will invest 100 trillion won, equivalent to $64.5 billion, to build new chip-making facilities in central Korea as part of its previously announced 1.1 quadrillion won chip expansion plan. Samsung Group and its affiliates also unveiled follow-up plans, worth 140 trillion won, for the region under their combined 2.655 quadrillion won project.

"The memory supercycle is undeniable," Christy Tan, global investment strategist at Franklin Templeton Institute, said in a note. "The issue is that the index has become increasingly narrow."

Stripping out Samsung and SK Hynix, the market returned only about 5% in May, compared with 29% for the overall index, according to Tan.

"That is not broad market strength; it is concentrated semiconductor momentum," Tan said.

Write to Kwanwoo Jun at kwanwoo.jun@wsj.com

(END) Dow Jones Newswires

July 02, 2026 06:19 ET (10:19 GMT)