A wafer fab (fabrication facility) is a semiconductor manufacturing plant where silicon wafers are processed into integrated circuits. Scale: Multi-billion dollar facilities. Fabs cost 10-20+ billion USD for leading-edge nodes. Environment: Cleanroom environment (Class 1-10), controlled temperature/humidity, vibration isolation. Process flow: Wafers go through hundreds of process steps over weeks to months. Photolithography, etching, deposition, implantation, metrology. Capacity: Measured in wafer starts per month (WSPM). Large fabs: 50-100K WSPM. Node technology: Named by process node (5nm, 3nm). Smaller = more transistors, higher performance, more challenging. Major fab operators: TSMC (largest), Samsung, Intel, GlobalFoundries, SMIC, UMC. Foundry model: TSMC and others manufacture for fabless companies (NVIDIA, Apple, AMD) who design but dont own fabs. Equipment suppliers: ASML (lithography), Applied Materials, Lam Research, KLA. Location factors: Talent, supply chain, government incentives, water/power availability, seismic stability. Significance for AI: All AI chips (GPUs, TPUs, custom accelerators) manufactured in wafer fabs. Fab capacity constrains AI hardware supply.