Patent ID: 7189629

Claim:
A method for isolating semiconductor devices, comprising the steps of: forming a pad layer including at least one pad nitride film on a semiconductor substrate; forming a trench by etching the semiconductor substrate to a predetermined depth using the pad layer as an etch barrier; forming a sacrificing oxide film on a front surface including the trench; forming a nitride sidewall on the sacrificing oxide film at a sidewall of the trench; performing impurity ion implantation on a bottom of the trench exposed to an outside of the sidewall of the nitride film so as to increase an oxidation rate thereat; performing heat treatment for activating implanted ion impurities; removing the nitride sidewall and the sacrificing oxide film; growing a liner oxide film on both the bottom and the sidewall of the trench; forming a nitride film on the liner oxide film so as to fill the trench; and smoothing the isolation film.