Closing prices are displayed on monitors at the dealing room of Hana Bank's headquarters in Seoul on Friday, when SK hynix hit its upper price limit. [Yonhap]
Closing prices are displayed on monitors at the dealing room of Hana Bank's headquarters in Seoul on Friday, when SK hynix hit its upper price limit. [Yonhap]

Renewed optimism over AI investment spending drove South Korea's two leading semiconductor stocks to record single-day gains on Friday. SK hynix, the country's second-largest company by market capitalization, closed at its upper price limit for the first time in roughly 17 years since 2009.

Blowout earnings from US hyperscalers Microsoft and Amazon sparked a sharp rebound in investor sentiment, drawing massive buying from foreign and institutional investors. Both stocks recovered most of the ground lost over the previous three trading sessions, and the Kospi's total market cap expanded sharply in a single day.

Samsung Electronics surged 26.81% to close at 262,500 won ($182), while SK hynix rose 29.95% to hit its upper limit at 1.72 million won — both all-time record single-day gains. For SK hynix, it was also the first time the stock hit its upper limit since the daily price-move ceiling was widened from 15% to 30% in June 2015.

The two stocks in effect erased their losses from the previous three trading sessions — Samsung Electronics had fallen 19.34% and SK hynix 29.9% over that stretch. SK hynix recovered 94.6% of its three-session decline, while Samsung Electronics fully recouped its losses.

Compared with Thursday, the market caps of Samsung Electronics and SK hynix surged by 327 trillion won and 288 trillion won, respectively. Samsung Electronics' market cap crossed 1,530 trillion won, re-entering the $1 trillion club and climbing to 12th globally, while SK hynix's market cap reached 1,255 trillion won, lifting it to 18th place worldwide.

The two stocks topped the net purchase rankings for both foreign and institutional investors. Foreign investors net-bought SK hynix and Samsung Electronics worth 3.61 trillion won and 2.12 trillion won, respectively, for a combined total of more than 5.7 trillion won. Institutional investors purchased 931.8 billion won of Samsung Electronics and 544.6 billion won of SK hynix.

The combined share of the two stocks in the Kospi's total market cap rose from 46% on Thursday to 51%, and the Kospi's overall market cap grew 18% in a single session.

Strong overnight earnings from hyperscalers — large-scale data center operators — including Microsoft and Amazon turned lingering doubts about AI investment into conviction, igniting a surge in buying sentiment.

The Philadelphia Semiconductor Index, which tracks 30 major US-listed chip stocks, jumped 8.19% on the day. Micron led the gains with an 18.36% advance, while SanDisk and AMD rose 25.99% and 13.00%, respectively, and Intel climbed 11.30%.

Bargain hunting after the recent steep declines also appeared to fuel the rally. Both stocks opened with gains of around 25%, triggering static volatility interruption devices — which temporarily switch trading to a single-price auction for two minutes — immediately after the opening bell.

SK hynix drew additional momentum from two developments on Thursday: a regulatory disclosure that SK Group Chairman Chey Tae-won had bought 3,620 common shares on the open market, and news that the company's American depositary receipts had surged 17.52% overnight on the New York Stock Exchange.

Chey's weighted-average acquisition price was disclosed at 1.35 million won per share, putting the total value of his Thursday purchase at approximately 4.9 billion won. With Friday's surge in SK hynix's share price, his one-day paper gain on that purchase alone was estimated at around 1.3 billion won.


th5@heraldcorp.com