diode protection antenna
to make a super flat device layer structure, moder processing use a lot of CMP (chemical mechanical polishing) process (CMP), the wafer will swirl at high speed under certain atmosphere, during which static charge will accumulate on anything that does not have a path to ground on top of wafer, the metals which is hooked up with CMOS device gate is a good target, if the accumulated charge is too much, then the big voltage potential between the gate and channel will break it. meanwhile all the meatals hooked up with the source/drain will not have this problem since the charge can find a path to substrate and will not accumulate.