Patent ID: 8536017

Claim:
A method of manufacturing a semiconductor device, comprising: forming a pad insulating film over the main surface of a semiconductor substrate; successively processing the pad insulating film and the semiconductor substrate in a predetermined region to form a plurality of trenches including a first trench having a width of 0.2 μm or less and a second trench having a width of 1.0 μm or more; thermally oxidizing the side surface and the bottom surface of each of the trenches; applying a solution containing polysilazane onto the main surface of the semiconductor substrate including the inside of the trenches by using the method of application to form a first polysilazane film as a first insulating film to be buried in the trenches; applying a solution containing polysilazane to the upper surface of the first polysilazane film by using the method of application to form a second polysilazane film; carrying out a heat treatment at from 300° C. to 800° C. in a water vapor atmosphere to convert the first polysilazane film into a silicon oxide film, thereby forming a first buried oxide film and at the same time, convert the second polysilazane film into a silicon oxide film, thereby forming a second buried oxide film; polishing the surface of each of the first buried oxide film and the second buried oxide film to planarize the same; and after the polishing of the surface, removing the pad insulating film, wherein in the applying of the solution containing polysilazane onto the main surface, the first trench is completely filled with the first polysilazane film and the second trench is not completely filled with the first polysilazane film.