Samsung Electronics and SK Hynix both plummeted by 13% to 14% at the close today (the 28th).

In the main bourse, Samsung Electronics finished down 13.39% at 220,000 won, while SK Hynix closed 14.65% lower at 1,550,000 won.

This marks the first time Samsung Electronics has closed in the 220,000-won range in about three months since April 30.

SK Hynix also regressed to levels last seen in early May.

In particular, Samsung Electronics recorded its largest drop of the year and the fourth-largest in its history.

For SK Hynix, it marked the second-largest decline this year.

The drop was less than a percentage point away from SK Hynix's all-time record decline of 15.37% set on the 13th.

Foreign investors were the biggest sellers, offloading a net 3.2092 trillion won worth of SK Hynix shares in a single day.

Samsung Electronics came in second, with foreign investors dumping 1.6341 trillion won, also in the trillions.

Although institutional investors were the top net buyers of SK Hynix, their purchasing volume stopped at around 907.7 billion won, falling short of offsetting the sell-off.

Analysts attribute the downturn to news that China has begun mass production of core semiconductor manufacturing equipment, alongside persistent concerns over AI circular investment.

Overnight, a U.S. online media outlet reported that China has entered mass production of deep ultraviolet (DUV) lithography equipment for semiconductor manufacturing, which is the previous generation of extreme ultraviolet (EUV) lithography equipment primarily produced by Dutch semiconductor equipment maker ASML.

In response, Choi Seol-hwa, a researcher at Meritz Securities, noted, "It appears that remarks made by a professor at a Chinese transportation university during an internal meeting last month became belatedly known. Since the specific company has not been disclosed, verification of the actual progress is necessary."

She added, "Opinions among Chinese institutions regarding domestic DUV equipment also seem mixed. Currently, the annual production scale is estimated at fewer than several dozen units, showing a wide gap with ASML's annual supply. Achieving 100% localization of all components is difficult, and there is a view that it is still in the testing phase."

Following this news, semiconductor investment sentiment weakened overnight on Wall Street amid concerns over intensifying global competition, including from China.

ASML plunged nearly 6%, and Nvidia declined by about 5%.

SK Hynix's American Depositary Receipts (ADRs) dropped 7%, while Micron and SanDisk fell over 2% and 11%, respectively.

(Photo: Yonhap News)