What is a semiconductor fab?
Short answer
A semiconductor fabrication plant, or fab, is a factory that makes integrated circuits (chips) by patterning and layering materials on silicon wafers in an ultra-clean environment. Building a leading-edge fab costs many billions of dollars.
What happens inside
Chips are built on thin discs of silicon called wafers. A wafer goes through hundreds of steps that are repeated layer by layer: depositing thin films, coating with light-sensitive material (photoresist), exposing patterns with light in photolithography, etching away material, and adding impurities (doping) to change electrical properties. Afterwards wafers are cut into individual dies, which are tested and packaged.
Fabs run in cleanrooms because a single speck of dust can ruin a circuit at these dimensions.
Foundries, IDMs and fabless companies
An integrated device manufacturer (IDM), such as Intel or Samsung, designs and makes its own chips. A fabless company, such as Nvidia, AMD or Qualcomm, designs chips but pays a foundry to manufacture them. A foundry, such as TSMC, makes chips for other companies. ASML is the supplier of the extreme ultraviolet (EUV) lithography machines used for the most advanced chips.
What "3 nm" and other nodes mean
Manufacturing generations are called process nodes and named with figures such as "5 nm" or "3 nm". Today these figures are marketing labels that signal a newer generation with generally higher density and efficiency; they are not a literal measurement of any single feature on the chip.
Why fabs appear in the news
Fabs take years and many billions of dollars to build, and few companies can make the most advanced chips, so capacity, location and government subsidies for new plants are recurring topics. Chip supply affects products from phones to cars to AI servers.