[Edaily Reporter Shin Ha-yeon ] The KOSPI rebounded from early-session weakness on the 1st to close nearly 2% higher at the 6,970 level. Institutional buying supported the index’s rise as Micron’s earnings and guidance, which exceeded market expectations, boosted investor sentiment in the semiconductor sector. The KOSDAQ surged more than 4%, driven by simultaneous buying from foreign and institutional investors, bringing it very close to the 900 mark.

According to MP Doctor on the 1st, the KOSPI closed at 6,971.35, up 133.31 points (1.95%) from the previous trading day. The index opened at 6,814.49, down 0.34% from the previous session, and fell as low as 6,765.06 during the session before rebounding sharply.

In terms of supply and demand, institutional investors were net buyers of 334.4 billion won on the stock market. In contrast, retail investors and foreign investors were net sellers of 1.4306 trillion won and 544.2 billion won, respectively. Program trading, combining arbitrage and non-arbitrage trades, recorded a net selling position of 373.3 billion won.

Among the top market capitalization stocks, SamsungElectronics(005930)closed at 276,000 won, up 2.79% from the previous trading day. SK hynix(000660)closed at 1,833,000 won, up 3.21%. SamsungElectronics(1P)(005935)(4.76%), SKSQUARE(402340)(1.40%), SamsungElectroMechanics(009150)(3.17%), LG Energy Solution(373220)(0.98%), HyundaiMotor(005380)(1.16%), and SAMSUNG BIOLOGICS(207940)(2.73%) also posted gains. On the other hand, KB Financial Group(105560)fell 1.66%.

This is interpreted as a resurgence of optimism regarding the memory market, following U.S.-based Micron’s announcement last night of earnings and guidance that exceeded market expectations. As confirmation emerged that demand for High-Bandwidth Memory (HBM) remains robust—driven primarily by investments in artificial intelligence (AI) data centers—buying interest also flowed into domestic semiconductor stocks.

Micron reported revenue of $54.23 billion and adjusted earnings per share (EPS) of $33.42 for the fourth quarter of fiscal year 2026, exceeding market expectations. The revenue forecast for the next quarter, at $61.5 billion, also significantly exceeded market expectations. In particular, driven by AI demand, the value of long-term supply contracts with customers increased from $22 billion in June to $32 billion.

Strong domestic semiconductor exports also bolstered investor sentiment. According to the Ministry of Trade, Industry and Energy, semiconductor exports in September reached $60.3 billion (81.9356 trillion won), a 262.8% increase from the same month last year, setting yet another all-time high. Exports of memory semiconductors reached $54.07 billion (73.4703 trillion won), a 358.6% increase year-over-year, while exports of system semiconductors rose 28.8% to $5.54 billion (7.5278 trillion won). This is interpreted as raising expectations for the domestic semiconductor industry, driven by robust demand for memory semiconductors amid expanding AI investment, coupled with Micron’s strong earnings.

On the KOSPI, 521 stocks rose, while 355 fell. Forty stocks closed unchanged.

By sector, medical and precision instruments rose by around 5%, and pharmaceuticals, electrical and electronics, securities, manufacturing, metals, machinery and equipment, textiles and apparel, IT services, transportation equipment and parts, general services, electricity and gas, distribution, transportation and warehousing, and paper and wood all closed higher. In contrast, sectors such as chemicals, food & beverages and tobacco, construction, real estate, finance, non-metals, insurance, entertainment and culture, and paper and wood closed lower.

On the same day, the KOSDAQ Index closed at 894.29, up 38.38 points (4.48%) from the previous trading day. The index opened at 853.96 and dipped as low as 851.92 early in the session, but subsequently turned higher, reaching a high of 894.29 before closing.

In the KOSDAQ market, foreign and institutional investors drove the index higher with net purchases of 230.8 billion won and 568.2 billion won, respectively. Retail investors engaged in profit-taking, recording net sales of 776.1 billion won. Program trading showed a net buying position of 415.6 billion won.

Among the top market-cap stocks, Alteogen Inc.(196170)(4.13%), ECOPRO CO., LTD(086520)(5.58%), ECOPRO BM CO., LTD.(247540)(5.13%), JUSUNG ENGINEERING Co.,Ltd.(036930)(3.66%), Rainbow Robotics(277810)(5.02%), WONIK IPS Co.,Ltd.(240810)(9.13%), and EO Technics Co., Ltd.(039030)(8.46%) all posted strong gains.

Kang Jin-hyuk, an analyst at Shinhan Investment Securities, noted, “Semiconductor materials, parts, and equipment stocks rose following Micron’s upward revision of its capital expenditure (CapEx) guidance, and biotech and rechargeable battery stocks also joined the rally.” He added, “As large-cap biotech and rechargeable battery stocks generally performed strongly, the KOSDAQ outperformed the KOSPI.”