Fab vs Foundry
"Fab" and "foundry" get used as if they're the same word, and in casual conversation that's harmless, but they actually answer two different questions. A fab is a place — a fabrication facility, the physical building full of lithography scanners, etch chambers, and cleanrooms where wafers get processed. A foundry is a business relationship — a company that runs fabs specifically to manufacture chips that other companies designed. Every foundry operates fabs, but not every fab belongs to a foundry.
"Fab" is short for fabrication facility, and it says nothing about who the customer is. Any building where silicon wafers move through deposition, lithography, etch, and metrology to become finished chips is a fab, whether it makes chips only for its own parent company or for a hundred outside customers. When an engineer says "the fab is down for maintenance," they mean the physical plant — the term carries no information about the business model behind it.
"Foundry" describes a customer relationship, not a piece of real estate. A foundry is a company whose fabs exist to manufacture designs that other, "fabless," companies own — the foundry never puts its name on the finished chip and, in the pure-play model, never designs or sells a competing product of its own. TSMC, the world's largest foundry, does not design GPUs or phone chips; it turns Nvidia's, Apple's, and Qualcomm's finished layouts into wafers and hands the finished dice back.
Lithography, etch, and every other process step happen the same way regardless of which label applies. The scanners printing 13.5-nanometer EUV light onto a wafer do not know or care whether the design belongs to the fab's own parent company or to an outside fabless customer — the physics and the process recipe are identical either way. "Fab" versus "foundry" is a question about the business wrapped around the building, never a question about what happens on the factory floor inside it.
The lines have blurred as integrated device manufacturers chase outside customers. Intel ran its fabs exclusively for its own chips for decades before opening Intel Foundry to external designs; Samsung's fabs simultaneously build Samsung's own Exynos chips and take on outside foundry customers from the same production lines. This is why a single company can now be an IDM and a foundry at once, and why the cleanest way to describe any given fab is by what it is running today, not by a fixed label attached to its owner.
| Term | What it actually describes | Example |
|---|---|---|
| Fab | The physical wafer-processing facility, any owner | Any building with litho, etch, and deposition tools |
| Foundry | A company that fabs designs owned by other companies | TSMC, GlobalFoundries, UMC, SMIC |
| IDM | A company that fabs mainly its own designs | Classic Intel, Samsung LSI, Micron, SK hynix |
| Foundry fab | A specific fab run under the foundry business model | Any TSMC or Intel Foundry production fab |
Read "fab" and "foundry" through a building-versus-business lens: the fab is the noun for the place, the foundry is the noun for who the place serves, and once that distinction is fixed, phrases like "Intel is opening its fabs to foundry customers" or "that fab used to be IDM-only" stop being confusing — they are simply describing the same physical building acquiring a new business relationship with the outside world.