Patent ID: 7374976

Claim:
A method for fabricating a thin film transistor, comprising: forming a first amorphous semiconductor film; forming a material including a metal element to promote crystallization over the first amorphous semiconductor film; heating the first amorphous semiconductor film to form a first crystalline semiconductor film; forming a second amorphous semiconductor film over the first crystalline semiconductor film by sputtering while a magnetic field is applied to a target using a magnet in a chamber; heating the first crystalline semiconductor film and the second amorphous semiconductor film; and removing the second amorphous semiconductor film, wherein the second amorphous semiconductor film serves as a gettering sink, and wherein the second amorphous semiconductor film comprises nitrogen at a concentration of 1×10 18 atoms/cm 3 or lower, oxygen at a concentration of 8×10 19 atoms/cm 3 or lower, and noble gas at a concentration of 1×10 20 atoms/cm 3 or higher.