Patent ID: 7553716

Claim:
A method for manufacturing a semiconductor device, said method comprising: forming an amorphous semiconductor film on an insulating surface; providing at least a portion of said amorphous semiconductor film with a crystallization promoting material comprising a metal element; crystallizing the amorphous semiconductor film by heating wherein the metal element diffuses into the semiconductor film during crystallization; forming an amorphous silicon second film comprising amorphous silicon over the crystallized semiconductor film, said amorphous silicon second film containing an impurity; diffusing the metal element into the amorphous silicon second film from the crystallized semiconductor film after completion of the formation of the amorphous silicon second film; and removing the amorphous silicon second film after diffusing the metal element into the amorphous silicon second film; wherein, after the completion of the diffusion of the metal element, a crystallinity of the amorphous silicon second film is lower than a crystallinity of the crystallized semiconductor film.