Depletion mode MOS capacitor with patterned Vt implants

摘要

A method for making a memory cell (10) in a process in which both an n-channel MOS transistors (12) and a p-channel transistor (44) are formed in a semiconductor substrate (30) is presented. The method includes implanting an impurity (40) into a region of the substrate (30) to form a part of a depletion NMOS memory capacitor (21) to be associated with the n-channel MOS memory transistor (12). The implant is performed concurrently with a patterned implant with the same impurity to adjust the threshold and punch-through of the p-channel transistor (44).