The day after Micron’s earnings, the memory trade fully ignited. On June 26, 2025, Reuters reported Micron shares climbing as investors bet that strong AI-related memory demand would carry into the second half of the year. At the same time, the Korean press recorded another milestone: SK hynix’s market capitalization hit an all-time high of about $157 billion.
Two events in the same week amplified the same signal: HBM supply is sold out, AI memory demand shows no ceiling, and capital is starting to reprice the big three memory makers as growth stocks rather than cyclical ones.
The earnings had already written the script: HBM sold out for calendar 2025, an annualized HBM run rate above $6 billion, and Q4 guidance of $10.7 billion. The June 26 price action was the market’s first vote on that script.
Micron: how the money reacted
On earnings night, the stock popped in extended trading and then gave back most of the gains — CNBC noted the market’s caution toward a stock that had already run hard. By Thursday, though, Reuters found the buyers back: the focus had shifted to the long-term AI memory demand story rather than quarter-to-quarter profit taking.
From the start of the year through the last trading day before the report, Micron shares were up 51 percent, against 3.4 percent for the Nasdaq. The information from the earnings and the call — HBM sold out for 2025, an annualized HBM run rate above $6 billion, and a target to match HBM share to overall DRAM share in the second half of 2025 — all pointed to a rally with fundamental support, not momentum chasing. What supports the call is visibility: with sell-outs and long contracts, memory revenue can be projected a year ahead for the first time.
SK hynix: a record market cap
The same day, Korea JoongAng Daily reported that SK hynix’s market capitalization hit an all-time high of roughly $157 billion, bringing its value contest with Micron to close quarters. That is a new kind of sensitivity for memory stocks. As the leading supplier in HBM, SK hynix has been one of the most direct beneficiaries of the AI memory rally.
The record is, at its core, the market pricing in HBM leadership. With Micron declaring HBM supply sold out and allocations locked through 2026, the gap between the big three memory makers breaks down into two questions: whose HBM capacity ramps faster, and who gets to hold the AI customers’ long-term contracts. The share-price action in late June suggested the market had already started answering. The same logic is being discussed around Samsung: the gap between chaser and leader is, for once, visible in market caps.
Memory becomes the main battleground of AI hardware
The deeper story is the changed status of memory in AI hardware. HBM is co-packaged with GPUs and constrained by advanced packaging capacity, so customers must lock supply a quarter or more in advance. Micron’s “sold out” declaration confirmed that, for the first time in the AI era, memory makers hold real supply-side leverage.
Compare 2023, when the industry was still cutting production through a glut, and the mid-2025 inflection is stark: the same companies with the same product lines, re-rated from cyclical stocks to growth stocks by a single demand engine — the AI data center. With visibility stretched from one quarter to a full year, memory makers can invest more aggressively in capex and R&D — and the contest after HBM4 will only be harsher. What capital is repricing is not an inventory restock but the long-term supply discipline of HBM.
What to watch next
Three things matter in the short term: whether Micron delivers its $10.7 billion fiscal Q4 revenue guidance (quarter ending in August); the sampling and mass-production cadence of SK hynix’s and Samsung’s HBM4; and the price and volume of 2026 HBM supply negotiations — all to be revealed over the next two quarters of earnings and supply-chain reporting.
For teams buying AI infrastructure, memory has become a bottleneck variable on par with GPUs. Building HBM supply cycles into capacity planning is the most practical lesson of the late-June 2025 rally. Whether the move proves event-driven or structural is what the next two quarters of earnings will decide.
Sources
- Reuters: Micron shares rise on bets of strong demand for AI-related memory chips
- Korea JoongAng Daily: SK hynix hits record $157B market cap, checking shoulder for Micron
- CNBC: Micron fiscal Q3 2025 earnings report
AI-assisted summary compiled from the sources above, reviewed by a human before publishing.