SK Hynix shares rose as much as 12% in Seoul on Monday, making the South Korean memory specialist the second-most valuable company on the KOSPI, behind only Samsung Electronics. The rally, driven by foreign buying following strong earnings and reaffirmed AI infrastructure plans from US hyperscalers, reflects a market increasingly focused on high-bandwidth memory (HBM) as the critical component in AI servers.
The trigger: hyperscaler capex
Big Tech’s combined 2026 capital expenditure is on track to land between $650bn and $725bn, an increase of roughly 77% on 2025. Microsoft has guided to as much as $190bn for the calendar year, with its CFO attributing about $25bn of that to rising memory-chip and component costs. Meta raised its own range to $125–145bn, citing similar pressures. Amazon’s Andy Jassy has committed roughly $200bn. Google has not been quieter. A meaningful share of this spending lands in the bill of materials for HBM, where SK Hynix dominates.
Why SK Hynix dominates
By late 2025, SK Hynix held an estimated 57% of the global HBM market, according to figures cited by analysts at Counterpoint and others. That share is unusually concentrated for a commodity-adjacent business. SK Hynix’s first-quarter operating profit, reported on 23 April, was a record. Operating margins on its memory line, by some sell-side estimates, are running above 70%.
HBM is not ordinary DRAM. It is a stacked, 3D-packaged memory built to feed bandwidth-hungry GPUs, and producing it requires advanced packaging steps that the industry, including Samsung and Micron, has been slower to scale than buyers would like. According to TrendForce, both Samsung and SK Hynix have raised HBM3E prices by roughly 20% for 2026, and supply is being booked years in advance by hyperscalers and accelerator vendors.
Supply constraints and long-term deals
Samsung’s memory chief publicly warned earlier this year that significant memory shortages were likely to persist through 2027. The chairman of SK Group has gone further, telling investors he expects the wider chip-wafer constraint to last until 2030. Long-term supply agreements, in which a hyperscaler effectively reserves output years ahead, are becoming the norm. Reuters reports SK Hynix and Samsung increasingly signing such deals with Microsoft and Google directly.
Risks and dissenters
There are, predictably, dissenters. The CAPE ratio on US equities now sits around 38, a level last seen at