Patent ID: 8119493

Claim:
A method of forming a semiconductor device, the method comprising: forming a first groove in a semiconductor substrate; forming an insulating film in the first groove; forming an interlayer insulating film covering the first groove; and performing a removing process that removes a part of the interlayer insulating film and a part of the insulating film in the first groove to form an alignment mark in the first groove, wherein the forming the insulating film comprises: forming a first silicon oxide film on an inside wall of the first groove; forming a silicon nitride film partially filling the first groove; forming a second silicon oxide film over the silicon nitride, the second silicon oxide film being in the first groove, and wherein the removing process comprises: removing a part of the interlayer insulating film in a horizontal direction while removing a part of the first silicon oxide film, a part of the silicon nitride film, and a part of the second silicon oxide film in a vertical direction.