Method for forming a field oxide film of a semiconductor device

Abstract

A method for forming a field oxide film of a semiconductor device capable of minimizing the size of bird's beak and avoiding an occurrence of crystal defect at a semiconductor substrate. The methods comprises the steps of forming a first oxide film, a first polysilicon film and a nitride film, over a semiconductor substrate, and etching predetermined portions of the nitride film and the first polysilicon film to form a field oxide region, forming a first field oxide film in the field oxide region, etching the first field oxide film to form a round recess on the semiconductor substrate, and forming a second oxide film over the round recess of the semiconductor substrate, depositing a second polysilicon film over the resulting structure, and etching the second polysilicon film without using any mask to form polysilicon film spacers at side walls of the first oxide film, first polysilicon film, and nitride film forming the field oxide region, and growing a second field oxide film over the field oxide region, etching the nitride film and the first polysilicon film, etching the first oxide film and an upper portion of the second field oxide film, and smoothing the entire exposed surface of the resulting structure to form a third field oxide film.

Dependencies are inferred from the claim text.