Who makes silicon wafers for AI data centers

Silicon wafers are the physical substrate every chip in this layer starts from, sold to the advanced-node foundry step before any transistor is patterned onto them. It's a raw-materials position upstream of essentially the entire rest of the layer — every merchant GPU, custom ASIC, CPU, NIC, and DPU chip design traces back to a wafer order from one of a handful of specialty producers, most of them concentrated in Japan, Taiwan, Germany, and Korea. The investor case here is a volume and specification story rather than a differentiation story: wafer demand tracks foundry wafer starts, and AI accelerator dies, being larger and more complex than typical logic chips, add incremental pressure on the most advanced wafer specifications even when unit counts alone wouldn't suggest tight supply. Supplier concentration is high and the qualification bar for a new wafer supplier at an advanced node is steep, so this tends to be a stable, long-cycle relationship business rather than one with frequent competitive displacement.