SK hynix HBM3E 12-layer

What it is

HBM3E is SK hynix's fifth generation of high-bandwidth memory (HBM); the company describes it as an extension of HBM3 rather than a break with it^[1]. HBM is built by stacking memory dies vertically and wiring them together with through-silicon vias (TSVs), so a processor is connected to memory through a very wide interface instead of a narrow one. Conventional memory modules take the opposite approach, running a narrow bus at high frequency; HBM trades area and packaging complexity for bandwidth.

This item covers the twelve-die version. SK hynix announced on 26 September 2024 that it had begun mass production of 12-layer HBM3E, and said it was the first company to do so^[1].

What the twelve layers change

The package holds 36 GB, the largest capacity among HBM products at the time. The previous eight-layer HBM3E held 24 GB, built from eight 3 GB DRAM dies, so the new part carries 50% more capacity^[1].

The extra capacity does not come with a taller package. SK hynix made each DRAM die 40% thinner, so the twelve-layer stack keeps the same overall thickness as the eight-layer one^[1]. More layers and thinner dies make heat and mechanical stress inside a stack harder to manage; SK hynix said the new stack also improved heat dissipation by 10%^[1].

The dies are joined by through-silicon via stacking together with the company's advanced MR-MUF process, which injects a protective material between the stacked chips and hardens it^[1]. That material fills the gaps between layers and is part of how the package is held together and kept cool.

Thickness is a practical constraint rather than a cosmetic one: a stack has to fit within the height its package and the board allow, so adding layers without growing taller means each layer gives up some of its own thickness.

Speed

SK hynix lifted the operating speed to 9.6 Gbps^[1]. To give the figure a concrete meaning, the company said a GPU carrying four HBM packages could read all 70 billion parameters of the Llama 3 70B model 35 times per second^[1].

The example points at what memory bandwidth does for a large model. When a model runs, its parameters sit in memory and have to be pulled into the processor again and again; how fast they can be read sets much of the pace at which the model can work. Wider, faster memory raises that ceiling.

Where it sits

The launch came six months after SK hynix became the first company to supply 8-layer HBM3E, in March 2024^[1]. The two dates mark a short interval between the first supply of an eight-layer part and mass production of a twelve-layer one.

The capacity lead held: in 2025 SK hynix still described its 36 GB HBM3E package as the highest-capacity HBM product on the market^[2].