SK hynix overtook Samsung Electronics on Monday to become South Korea's most valuable listed company, the first time Samsung has surrendered the top spot on the KOSPI index since November 2000, according to Reuters. SK hynix shares closed up 5.6% to lift its market capitalization to 2,080.4 trillion won ($1.35 trillion), edging past Samsung's 2,066.7 trillion won excluding preferred shares, after a rally of more than 340% this year built almost entirely on demand for the high-bandwidth memory it supplies to Nvidia and other AI chip buyers. The company held 61% of the global HBM market in 2025, against 17% for Samsung and 21% for Micron.

SK hynix is one of the few pure-play memory makers, while Samsung spans smartphones, displays, contract chipmaking, and home appliances, among many other markets. Investors value the focus on pure-play memory higher because HBM carries the industry's fattest margins and ties suppliers to specific AI accelerators, unlike commodity DRAM that buyers can swap between vendors.

SK hynix built its lead by continuing to invest in HBM through the 2023 downturn, when a memory price collapse pushed it to a 7.73 trillion won annual operating loss. Samsung, by contrast, reportedly hit yield and qualification delays on its HBM3E chips that slowed major Nvidia orders, the proximate reason for a 61% share against a 17% one.

Samsung's remaining stronghold is conventional DRAM, but even that margin is shrinking. Bank of America estimates put SK hynix's monthly DRAM output at roughly 589,000 wafers this year against Samsung's 691,000. SK hynix is projected to expand output by about 38% between 2025 and 2028, compared with 17.5% at Samsung, which would cut the production gap to under 10% by 2028 from around 23% in 2025. The capacity both companies are pouring into HBM is not going into the commodity chips behind the memory shortage they've warned could run past 2027, and SK hynix has pledged to double its memory wafer output within five years.

Samsung, meanwhile, disputes the ranking, telling Reuters that its market cap should include preferred shares, which would lift its value to 2,246.4 trillion won. The gap also reflects the HBM3 and HBM3E generations rather than what comes next. Nvidia CEO Jensen Huang confirmed earlier this month that Samsung, SK hynix, and Micron all passed HBM4 certification for the Vera Rubin platform, and Samsung shipped the industry's first 12-layer HBM4E samples on May 29th.

SK Group Chairman Chey Tae-won, who pushed through the original Hynix acquisition despite internal opposition, explained the strategy in a book published in January. "What I really wanted to accomplish when we acquired Hynix was to transform it from a commodity memory producer into a mainstream semiconductor company whose products are indispensable," Chey said.

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Luke James is a freelance writer and journalist.  Although his background is in legal, he has a personal interest in all things tech, especially hardware and microelectronics, and anything regulatory.