Patent ID: 7670907

Claim:
A method of forming a memory device, comprising: forming a first dielectric layer on a semiconductor substrate; forming a protective cap layer overlying the first dielectric layer; forming and patterning a hard mask layer overlying the protective cap layer, the patterned hard mask layer exposing two or more areas of the protective cap layer, the first dielectric layer, and the substrate for future isolation regions of the memory device; removing portions of the protective cap layer, the first dielectric layer and the substrate in the areas for future isolation regions, thereby forming two or more trenches; forming a second mask layer overlying a first portion of the hard mask layer and at least one first trench in a memory array portion of the memory device, leaving a second portion of the hard mask layer and at least one second trench uncovered in a periphery of the memory device; removing additional substrate material from the at least one second trench so that the at least one second trench is deeper than the at least one first trench; removing the hard mask layer and the second mask layer substantially concurrently; filling the at least one first trench and the at least one second trench with a dielectric material to respectively form at least one first isolation region in the memory array portion and at least one second isolation region in the periphery; removing the protective cap layer; forming a second dielectric layer overlying the substrate and on the at least one first isolation region and the at least one second isolation region; and forming a first conductive layer overlying the second dielectric layer.