ASML & TSMC
ASML is the sole manufacturer of EUV (extreme ultraviolet) lithography machines in the world, holding over 90% of the EUV market and 62% of all photolithography equipment. TSMC is ASML's largest single customer, purchasing the majority of ASML's annual EUV machine output to manufacture chips at 7nm and below for NVIDIA, Apple, AMD, and every other advanced chip designer.
Why it matters: Without ASML's EUV machines, no chip can be manufactured below 7nm. There is no alternative supplier anywhere in the world. TSMC's process leadership, which underpins the AI chip revolution, is therefore directly dependent on a single Dutch company whose core technology took 30+ years and $9B+ in collective R&D investment from ASML, Intel, and TSMC to develop.