Patent ID: 7442598

Claim:
A method for forming a semiconductor device comprising: providing a semiconductor substrate; forming a first stressor layer of silicon-lean silicon nitride over a surface of the semiconductor substrate, wherein the first stressor has compressive stress; selectively removing portions of the first stressor layer to leave a remaining portion; forming a second stressor layer of silicon-lean silicon nitride over the surface of the semiconductor substrate and the remaining portion of the first stressor layer, wherein the second stressor layer has tensile stress; forming a photoresist layer over the second stressor layer; patterning the photoresist layer to leave a portion of the photoresist layer that overlaps the remaining portion of the first stressor layer and exposes a first portion of the second stressor layer; and applying a wet chemistry comprising hydrofluoric acid to the portion of the photoresist layer and the first portion of the second stressor layer, wherein wet chemistry comprising hydrofluoric acid is characterized by etching the second stressor layer at a greater rate than the first stressor layer.