Patent ID: 8003449

Claim:
A method for manufacturing a semiconductor device comprising the steps of: forming a first conductive layer made from aluminum as its main component by a sputtering method over a substrate; forming a second conductive layer made from a material different from that used for forming the first conductive layer over the first conductive layer, the second conductive layer having a higher heat-resistance property than the heat-resistance property of the first conductive layer; forming a gate electrode by patterning the first conductive layer and the second conductive layer; forming a gate insulating film over the gate electrode; forming a first semiconductor film over the gate insulating film; crystallizing the first semiconductor film by heating the first semiconductor film after introducing a catalytic element into the first semiconductor film; depositing a second semiconductor film including a first impurity element over the first semiconductor film; heating the first semiconductor film and the second semiconductor film, thereby gettering the catalytic element and a metal element mixed into the first semiconductor film in the step of forming the first semiconductor film; forming an island-shaped semiconductor region by patterning the first semiconductor film and the second semiconductor film; forming a third conductive layer over the island-shaped semiconductor region; forming a source electrode and a drain electrode by patterning the third conductive layer; and exposing a part of the first semiconductor film and forming a source region and a drain region within the island-shaped semiconductor region by etching the second semiconductor film with the source electrode and the drain electrode as masks within the island-shaped semiconductor region, wherein the first conductive layer includes carbon, and wherein the carbon of 0.1 to 10 atomic % is included.