The screens in Seoul turned red early and stayed that way. Korea’s KOSPI index fell more than 6% on Thursday, its steepest single-day decline in years, as investors dumped the semiconductor stocks that dominate the market. Samsung Electronics and SK Hynix, the country’s two largest companies and the world’s leading memory chip makers, each fell about 11%, dragging the broader index down with them.
The selloff was part of a global move rather than a Korean one. Semiconductor shares across Asia and the United States came under pressure this week as investors weighed whether the AI-driven demand that has powered the sector’s rally can continue at the pace the share prices imply. The trigger for the day’s selling was a combination of factors, according to analysts: a broad retreat from chip stocks, a new U.S. trade investigation into memory chips, and domestic political uncertainty in Korea.
The trade investigation added a specific worry. The U.S. International Trade Commission opened a probe into memory-chip patent infringement following a complaint from Netlist, a U.S. company that holds patents on memory module technology, according to reports. The investigation targets some of the largest memory makers, and its outcome could lead to import restrictions or licensing payments, adding a legal overhang to a business already dealing with volatile prices.
The political factor is harder to quantify but impossible to ignore. Korea has been through months of political turmoil, with the aftermath of last year’s martial law declaration still playing out in courts and in the streets, and investors have periodically sold Korean assets on the uncertainty. Each new episode reminds foreign funds that Korea’s equity market carries a political risk premium that its fundamentals do not fully explain.
For Samsung, the selloff arrives at an awkward moment in the product calendar. The company’s Galaxy Unpacked event is scheduled for July 22, where it is expected to unveil the Z Fold 8 and its latest foldable phones, the kind of product news that normally lifts sentiment around the stock. But in a market falling 6%, product launches do not move share prices, and analysts said the event would do little to counter the systemic selling.
The memory business is where the real questions lie. Samsung and SK Hynix together control most of the world’s supply of DRAM and NAND memory, and both have ridden the AI wave as demand for high-bandwidth memory, the specialized chips used in AI accelerators, has exploded. HBM prices have risen sharply, and both companies have posted record or near-record profits. The selloff this week was a reminder that even the best-positioned suppliers trade at multiples that assume the boom continues.
The vulnerability is structural. Memory is a commodity business with violent cycles, and the current upcycle has been driven by a single customer category, AI data center operators, whose spending decisions are concentrated among a handful of companies. Any slowdown in that spending, any inventory correction, or any shift in how AI chips are designed would hit Korean memory makers disproportionately. Investors who lived through the last downturn know how fast the cycle can turn.
The ITC investigation targets that business directly. Netlist’s patents cover technologies used in memory modules, and the company has a history of winning licensing deals and court victories against major memory makers. If the ITC finds infringement, it could block imports of the affected products into the United States, or require royalties that squeeze margins. Either outcome would be a tax on the exact products that have been driving Korean profits.
The day’s decline also had a mechanical element. Korean markets have a high proportion of retail investors, who trade heavily in the two chip giants, and margin positions unwind quickly when prices fall. The combination of global selling, a new trade probe and domestic politics created the kind of one-day cascade that Korean markets have experienced before, most recently during the 2024 political crisis.
The response from the companies has been muted. Samsung and SK Hynix have not commented on the selloff, and both are expected to stick to their stated plans for expanding HBM production. The ITC investigation will take months to play out, and both companies have legal teams that have fought similar cases before. The market’s mood, however, is not controlled by legal timelines.
The bigger question is what the selloff means for the AI trade. Korean chip stocks have been among the most popular ways for global investors to bet on AI hardware, and the fact that they are falling despite strong earnings, record guidance and full order books suggests that the marginal buyer has become cautious. Whether Thursday marks the start of a correction or just a noisy day will depend on whether the AI spending data that drove the rally continues to hold up.
For Korean policymakers, the day was a reminder of how concentrated the country’s market has become. Samsung and SK Hynix account for a large share of the KOSPI’s value, which means the fortunes of two companies, and one industry, decide the mood of the entire market. Diversification has been a policy goal for years, but the chip cycle keeps pulling the index back to the same two names.
The Galaxy Unpacked event next week will proceed as planned, and the foldables will get their moment. But the stock market’s attention is elsewhere, on trade probes, politics and the durability of AI spending. For Samsung and SK Hynix, the product news will have to wait for a calmer tape.
