Patent ID: 8053286

Claim:
A method of forming a semiconductor device, comprising: forming grooves in an insulating region and in a semiconductor region, with forming burrs near the boundary between the insulating region and the semiconductor region; selectively forming protection films on inside walls of the grooves except on bottom walls of the grooves; and carrying out a selective thermal process in the presence of the protection films, thereby removing the burrs, wherein selectively forming the protection films comprises: forming the protection film on the side and bottom walls of the grooves; carrying out an anisotropic etching process for etching the protection film, so that the protection film on the side walls of the groove is thicker than the protection film at the bottoms of the groove; and carrying out an isotropic etching process for etching the protection film, so that the protection film is removed from the bottoms of the grooves, while the protection film resides on the side walls of the grooves.