Patent ID: 7354834

Claim:
A method of forming a trench in semiconductor device, the method comprising: forming sequentially a pad oxide film and a silicon nitride film on an entire surface of a semiconductor substrate; forming the trench by etching the silicon nitride film and the semiconductor substrate up to a predetermined depth; forming a liner oxide film with a thickness thinner than that of the silicon nitride film on an inner wall of the trench; applying a negative voltage to a back surface of the semiconductor substrate such that the liner oxide film of the trench stores more positive charges the silicon nitride film, wherein applying the negative voltage includes using injecting electrons into the back surface of the semiconductor substrate using an electron gun; and forming a filling oxide film by atmospheric pressure chemical vapor deposition (APCVD) or subatmospheric chemical vapor deposition (SACVD) on a surface of the liner oxide film of the trench and the silicon nitride film by depositing a field oxide while the liner oxide film of the trench stores more positive charges than the silicon nitride film, wherein a deposition rate of the field oxide on the liner oxide film of the trench is higher than a deposition rate of the field oxide on the silicon nitride film.