Sector VI · 6 chokepoints · 20 names

Memory

The Memory Wall — HBM, DRAM, NAND & the AI Memory Cartel

Imagine an AI chip as a very fast chef. The chef can chop, fry, and plate dishes faster than any human — but only if the ingredients arrive at the cutting board fast enough. If the pantry is across the kitchen and the runner is slow, the chef stands around doing nothing. The chef is the GPU. The pantry is the memory. The runner is the bandwidth between them.

For the past decade, the chefs (chips) got dramatically faster, but the runners (memory bandwidth) didn't keep up. That gap is called the "memory wall," and it's the single biggest reason modern AI is bottlenecked. The fix: stack a tower of memory chips literally on top of each other right next to the GPU, with thousands of tiny wires running between them. That's High Bandwidth Memory — HBM. Every NVIDIA Blackwell, every AMD MI300, every Google TPU, every Amazon Trainium needs 6–8 of these towers per chip.

Only three companies on Earth make HBM: SK Hynix, Samsung, and Micron . NVIDIA has bought essentially every HBM4 wafer for 2026 and 2027. Micron's CEO told CNBC in March 2026 they can only supply about half to two-thirds of what their biggest customers actually want. That is what a chokepoint looks like in real time. And the equipment that stacks HBM (Hanmi's TC bonders) and tests every finished AI chip (Advantest) are even cleaner monopolies than the memory makers themselves.

Sources

Bernstein, TrendForce, Counterpoint · May 2026

The 6 chokepoints

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Choke 01

The HBM Oligopoly — Three Companies Make the World's AI Memory

HBM3E · HBM4 · HBM4E · Stacked DRAM

Three firms. ~95% of the world's AI memory. NVIDIA has bought all of 2026 and most of 2027 in advance.

HBM is not made the way regular memory is made. It is built by stacking 8 to 12 DRAM dies on top of each other, drilling thousands of tiny vertical wires through them ("through-silicon vias"), and gluing the whole tower to a GPU package . The yields are brutal, the equipment is exotic, and the design rules change with each generation. Only SK Hynix, Samsung, and Micron have mastered it at scale. Per TrendForce, HBM3E supply prices were raised nearly 20% for 2026 contracts; HBM4 has settled in the mid-$500s per stack — roughly 50% above HBM3E. Bernstein estimates HBM was over 50% of DRAM revenue in Q2 2026 (~$7.5B/quarter at SK Hynix alone).

Why this is a chokepoint

Every AI chip in production today needs HBM. There is no substitute. Building a new HBM line takes 18-24 months from first dollar to first revenue. With NVIDIA shipping millions of accelerators per year — each with 6 to 8 HBM stacks — the math simply does not work for demand to meet supply before 2027 at the earliest.

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000660.KS

SK Hynix

not US-tradable

~57% of global HBM revenue, ~70% of NVIDIA Rubin HBM4 allocation — the single most important memory company in the AI buildout.

The Korean DRAM and NAND maker that invented HBM in 2013 and has dominated the category ever since. They won the AI lottery by being first to mass-produce 8-high and 12-high HBM stacks at high yield, using a proprietary packaging process called MR-MUF (Mass-Reflow Molded Underfill) that runs cooler than Samsung's competing approach. Market cap crossed $1 trillion USD in May 2026. NYSE ADR listing confidentially filed with the SEC March 2026, targeting 2H 2026 debut.

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Micron Technology

Only US-based HBM maker. ~21% HBM share Q2 2025 (overtook Samsung). Crossed $1T market cap May 26, 2026.

The only US-headquartered memory maker — DRAM, NAND, and HBM. The "Made in America" HBM hedge for hyperscalers who need a non-Korean second source. Building new fabs in Boise, Idaho (HBM and leading-edge DRAM) and Clay, New York with CHIPS Act funding. HBM3E claimed 30% lower power than competitors per management. Per CEO Sanjay Mehrotra on CNBC's Squawk on the Street (March 19, 2026): "We are only able to supply, for our key customers in the midterm, about 50% to two-thirds of their requirements. The gap between demand and supply for all of DRAM, including HBM, is really the highest that we have ever seen."

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005930.KS

Samsung Electronics

not US-tradable

The comeback story in HBM. Lagged through 2024-25; now caught up. Targeting 50% HBM capacity expansion in 2026.

The Korean conglomerate that does everything — memory, foundry, smartphones, displays, consumer electronics. Memory + foundry is the AI-exposed piece. After being caught flat-footed on HBM3E qualification through 2024 and most of 2025, Samsung's HBM4 reportedly passed NVIDIA's 10-11 Gb/s qualification in early 2026, putting them back in the game. Foundry division vertically integrated with in-house SEMES TC bonders.

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