TSMC: The Partner That Answers Samsung's IntegrationNarrow moat

The most important thing about SK hynix's relationship with TSMC is that it is not a competitive relationship at all, and that is what makes it strategically interesting.

High-bandwidth memory is becoming a logic problem as much as a memory one. The base die at the bottom of the stack — the part that talks to the processor — is moving to a customer-configurable design built on a logic process, which is precisely the capability SK hynix does not have and Samsung does. SK hynix used a proprietary base die up to HBM3E and moved HBM4's onto TSMC's advanced logic process¹. SK hynix's response was to partner with TSMC for the base die rather than attempt to build a foundry, and the arrangement lets it offer a stack whose logic layer is made on the best available process without owning a single logic fab.

That is a genuinely good trade. It converts a structural disadvantage against a vertically integrated rival into a supplier relationship, and it does so with a foundry whose entire commercial promise is that it does not compete with its customers.

The dependency it creates is real and one-directional. SK hynix's most valuable product now has a critical layer it does not manufacture, made by a company with its own allocation decisions and its own list of customers — including, in other capacities, Samsung.

What to watch is whether the base die stays a shared design or becomes something each buyer specifies separately. The more customer-specific it gets, the more of the value migrates toward whoever makes the logic.