HBM (High Bandwidth Memory)

HBM (High Bandwidth Memory) is DRAM stacked vertically and placed beside a processor on the same package, connected through an interface thousands of bits wide. The JEDEC HBM4 standard reaches 2 TB/s of bandwidth per stack, which is why every AI accelerator pairs its GPU with HBM and why the chips command premium prices.

What is HBM?

HBM solves a geometry problem. A processor doing AI math is only as fast as the data it can pull from memory, and ordinary DRAM modules, sitting centimeters away in slots and connected over a 64-bit channel, cannot feed a modern GPU. HBM’s answer is to stack DRAM dies vertically, 4 to 16 high, drill them through with thousands of vertical connections, and mount the stack on the same package as the processor. The JEDEC HBM4 standard (JESD270-4), published April 16, 2025, runs 8 Gb/s across a 2,048-bit interface for 2 TB/s of total bandwidth per stack, with 32 independent channels and stack capacities up to 64GB (JEDEC). Each generation gets harder to build: SK Hynix, which completed the world’s first HBM4 development in September 2025, says the new generation improves power efficiency by more than 40% and AI service performance by up to 69% (SK hynix). The company framed the September 12, 2025 milestone in plain terms:

“Completion of HBM4 development will be a new milestone for the industry.”

— Joohwan Cho, Head of HBM Development, SK hynix (SK hynix newsroom)

How is HBM used in thematic investing?

HBM is the choke point that the Asia memory semiconductor concept is built around. Only SK Hynix, Samsung, and Micron can mass-produce it, and two of the three are Korean: SK Hynix holds roughly 62% of HBM shipments (Astute Group), and Samsung began the industry’s first HBM4 mass sales for Nvidia’s Vera Rubin platform in Q1 2026 (Samsung). That scarcity is what produced SK Hynix’s 72% operating margin in Q1 2026, including 7.78 trillion won of sales to Nvidia alone (SK hynix), and it pulls a whole equipment chain along with it, from Hanmi Semiconductor’s TC bonders that stack the dies to Tokyo Electron’s interconnect etch tools.

Related terms & concepts

FAQ

Who makes HBM?

Only three companies mass-produce HBM: SK Hynix, Samsung Electronics, and Micron. SK Hynix leads, with industry analysts putting its share at roughly 62% of HBM shipments through 2026 (Astute Group). It completed the world's first HBM4 development in September 2025 (SK hynix), and Samsung began the industry's first mass sales of HBM4 for Nvidia's Vera Rubin platform in Q1 2026 (Samsung).

How is HBM different from regular DRAM?

Both store bits in DRAM cells, but ordinary DRAM modules connect to a processor over an interface 64 bits wide, while HBM stacks 4 to 16 dies vertically and connects through 2,048 bits in HBM4, delivering up to 2 TB/s per stack (JEDEC). The stack sits beside the GPU on the same package instead of in separate slots, which shortens wires, raises bandwidth, and cuts power per bit moved. The cost is complexity: stacking and bonding make HBM far harder and more expensive to manufacture.

Why does HBM matter to investors?

HBM converts AI capex into memory-maker profit. Every AI accelerator needs several HBM stacks, and supply is limited to three producers, so pricing power concentrated dramatically: SK Hynix, the share leader, posted a 72% operating margin in Q1 2026 with 7.78 trillion won of sales to Nvidia alone (SK hynix). HBM demand also pulls through the equipment chain, from Hanmi Semiconductor's TC bonders to Tokyo Electron's interconnect etch tools, making it the central variable of the Asia memory semiconductor concept.

Sources & references

  1. JEDEC and Industry Leaders Collaborate to Release JESD270-4 HBM4 Standard · JEDEC Solid State Technology Association, 2025-04-16
  2. SK hynix Completes World's First HBM4 Development and Readies Mass Production · SK Hynix Newsroom, 2025-09-12
  3. Samsung Electronics Announces First Quarter 2026 Results · Samsung Electronics (Samsung Global Newsroom), 2026-04-30
  4. SK hynix Reports Q1 2026 Business Results · SK Hynix Newsroom, 2026-04-23
  5. SK Hynix holds 62% of HBM, Micron overtakes Samsung, 2026 battle pivots to HBM4 · Astute Group, 2026-01-15