Samsung Electronics, SK Hynix Jump About 20% as US Chip Rally, Chey Buy Boost Sentiment

Samsung Electronics Co. and SK Hynix Inc. jumped about 20% in early trading on July 31, lifted by an overnight rally in U.S. semiconductor stocks and news that SK Group Chairman Chey Tae-won had made his first open-market purchase of SK Hynix shares.

As of 9:20 a.m., Samsung Electronics was trading in the upper 240,000-won range, up about 20% from the previous session, while SK Hynix was up more than 20% at around 1.6 million won. Samsung Electronics preferred shares and SK Square Co. also posted double-digit gains.

The advance followed a broad rebound in chip stocks on Wall Street overnight. The Philadelphia Semiconductor Index rose 8.19%, its biggest gain since April 2025. Micron Technology Inc. climbed 18.36%, Sandisk Corp. surged 25.99%, Advanced Micro Devices Inc. rose 13.00% and Intel Corp. gained 11.30%. Microsoft Corp., after reporting strong earnings, jumped 15.51%, while SK Hynix's American depositary receipts ended 17.52% higher at $149.

Improving U.S. inflation data also supported risk appetite. The U.S. personal consumption expenditures price index for June fell 0.1% from the previous month, while the MSCI Korea ETF jumped 11.79%, pointing to strength in South Korean equities.

Some market participants also said options positions built up during the recent selloff helped magnify the gains.

Seo Sang-young, an executive director at Mirae Asset Securities Co., said U.S. chip stocks rebounded after posting steep declines for five straight sessions, aided by earnings from Samsung Electronics and Microsoft. Options-related flows then amplified buying and drove the semiconductor sector sharply higher. In recent sessions, those same flows had deepened declines, but on July 31 they instead extended the rally, he added.

Chey's share purchase also boosted investor sentiment. According to filings on the Financial Supervisory Service's electronic disclosure system, he bought 3,620 SK Hynix common shares on July 30. Based on the previous day's closing price of 1.322 million won, the purchase was worth about $3.46 million.

It was the first time Chey had directly purchased SK Hynix shares. He had previously controlled the company through SK Inc. and subsidiary SK Square without personally holding the stock. SK Square is currently SK Hynix's largest shareholder, with a 20% stake.

The purchase drew market attention because it came as SK Hynix shares were pulling back after the company reported record second-quarter earnings. Investors took the buy as a sign of confidence in the company's medium- to long-term competitiveness.

Meanwhile, buy-side sidecars were triggered on both the Kospi and Kosdaq on July 31 as chip shares rallied. Foreign investors led the gains with net purchases of more than 3 trillion won on the Kospi, while buying was concentrated in semiconductor stocks led by Samsung Electronics and SK Hynix.