[Edaily Reporter PARK MIN ] The domestic stock market was decimated on the 28th amid a sharp plunge in U.S. semiconductor stocks and concerns over competition from China in the semiconductor sector. At one point during the session, the KOSPI plunged nearly 11%, breaking below the 6,000 mark, while the KOSDAQ also fell by over 9%, dropping below the 700 mark during trading for the first time in one year and three months.

According to MP Doctor, the KOSPI closed at 6,023.66 at 3:30 p.m., down 732.09 points (10.84%) from the previous trading day. The index opened at 6,413.57 early in the session but quickly extended its losses, briefly dropping to 5,992.91 in the afternoon and breaching the 6,000 mark.

This marks the first time in three months—since April 14—that the 6,000-point level, considered a psychological support line, has been breached. Subsequently, some bargain-hunting buying emerged, allowing the index to recover the 6,000-point level before the market closed.

Foreign investors led the sharp decline by net selling 4.9592 trillion won worth of stocks. Institutions also joined the selling spree with net sales of 638.7 billion won. Meanwhile, retail investors net bought 4.3180 trillion won worth of stocks in a bid to buy on the dip, but their efforts only managed to slightly mitigate the decline.

The KOSPI’s plunge was led by the top two semiconductor stocks by market capitalization. SK hynix(000660)plummeted 14.65% to 1.55 million won, and SamsungElectronics(005930)fell 13.39% to 220,000 won, driving the index lower.

Automotive, secondary battery, and financial stocks were also unable to escape the downward trend. HyundaiMotor(005380)fell 9.68%, and LG Energy Solution(373220)dropped 5.71%. Financial stocks KB Financial Group(105560)and Samsung Life Insurance(032830)also fell by 4.29% and 8.51%, respectively, while SAMSUNG C&T CORPORATION(028260)(-10.16%), ShinhanFinancialGroup Co.,Ltd.(055550)(-3.90%), KIA CORPORATION(000270)(-6.60%), HD HYUNDAI HEAVY INDUSTRIES(329180)(-7.30%), and DOOSAN ENERBILITY(034020)(-8.74%) joined the downward trend.

In contrast, SAMSUNG BIOLOGICS(207940)rose 0.26% to close at 1,549,000 won, making it the only stock among the top market-cap companies to join the rally. This is interpreted as buying interest flowing into relatively defensive sectors amid a deepening aversion to risk assets across the broader market.

The KOSDAQ market closed at 705.85, down 59.01 points (7.72%) from the previous trading day, due to heavy selling by institutional investors. Although the index briefly dipped below the 700 mark during the session, it partially recovered its losses as bargain-hunting buying emerged toward the end of the session. This was the first time the index had fallen below the 700 mark during trading since April 16, 2025—a span of about one year and three months.

In terms of supply and demand, institutions led the index lower with net sales of 134.6 billion won. In contrast, retail investors and foreign investors engaged in bargain hunting, posting net purchases of 51.6 billion won and 85.9 billion won, respectively. Program trading recorded a net purchase of 1.3 billion won, combining both arbitrage and non-arbitrage trades.

Among the top KOSDAQ stocks by market capitalization, Alteogen Inc.(196170)(-4.97%), ECOPRO BM CO., LTD.(247540)(-7.87%), ECOPRO CO., LTD(086520)(-9.80%), Rainbow Robotics(277810)(-10.20%), and JUSUNG ENGINEERING Co.,Ltd.(036930)(-14.08%) all fell across the board.

Both the KOSPI and KOSDAQ markets showed signs of a sharp decline from the opening bell. Following the temporary suspension of program sell orders (sell-side sidecar) in both markets early in the session, the losses widened, triggering circuit breakers simultaneously.

This marks the eighth time this year that a circuit breaker has been triggered on the KOSPI and the 14th time in history. Notably, this is only the third time—including March 4 and June 8—that circuit breakers have been triggered simultaneously on both the KOSPI and KOSDAQ markets.

Analysts attribute this sharp decline to a sudden freeze in investor sentiment—triggered by news from the Chinese semiconductor sector and the fallout from the decline in U.S. semiconductor stocks—which led to a steep drop in the index.

Overnight on the New York Stock Exchange, NVIDIA plunged 4.99%, and the Philadelphia Semiconductor Index also fell 2.23% that day. In addition, shares of major semiconductor companies such as Micron, SanDisk, and AMD also declined. SK hynix American Depositary Receipts (ADRs) also fell 7.47%, dropping below their initial public offering price.

In particular, concerns over China’s “semiconductor rise” also weighed on the domestic stock market. Following the successful initial public offering (IPO) of Chinese memory chipmaker Changxin Memory (CXMT) the previous day (the 27th), news that China has begun developing deep ultraviolet (DUV) lithography equipment—a key component in semiconductor manufacturing—is believed to have further dampened investor sentiment toward the semiconductor sector.

Kim Seok-hwan, an analyst at MIRAE ASSET SECURITIES, stated in a report released that day, “The causes of this sharp decline can be summarized into three factors: concerns over China’s pursuit of semiconductor technology and expansion of supply; doubts about the profitability of increased investment in artificial intelligence (AI); and the forced reduction of positions that had been concentrated in domestic semiconductor stocks and single-stock leveraged products.”