Patent ID: 7056381

Claim:
A method for fabricating a semiconductor device, comprising: forming an insulating base film comprising silicon oxynitride oxide nitride over a substrate; forming an amorphous semiconductor film comprising silicon over the insulating base film; introducing a metal element which promotes crystallization of silicon to the amorphous semiconductor film comprising silicon; crystallizing said amorphous semiconductor film by a first heat treatment to obtain a crystalline semiconductor film comprising silicon; irradiating said crystalline semiconductor film with a light selected from laser light and intense light in order to diffuse said introduced metal element throughout said crystalline semiconductor film; gettering said metal element from said crystalline semiconductor film by implementing a second heat treatment within an oxidizing atmosphere after said irradiating, thereby a first thermal oxide film of said semiconductor film including said metal element is formed on said crystalline semiconductor film; removing said first thermal oxide film to expose a surface of said crystalline semiconductor film; patterning said crystalline semiconductor film after removing the first thermal oxide film; and forming a second thermal oxide film of said semiconductor film on the exposed surface of said crystalline semiconductor film by implementing a third heat treatment after said patterning, wherein a temperature of the first heat treatment is within a range of 550 to 650° C. and a temperature of the second heat treatment is within a range of 600 to 750° C.