What's diffused diode resistor?
The leftmost resistor, the POLY, is conductive gate oxide deposited atop THICK oxide, to withstand high voltages. At 100 ohms and 1,000 volts, there will be 10 amps dumped thru that first diode into the VDD, and probably into substrate if the diode is 3_layer.

The diffused_diode resistor has the task of dumping ESD energy into the substrate. The 2nd terminal of the diode is the Substrate (ground for this process) and by placing a large number of Substrate Contacts at some distance form the &quot;Diode&quot; anode contacts, the ESD energy is again steered into the substrate.