Semiconductor device

A semiconductor device having a thin film transistor comprising:

• a gate electrode over a substrate;
• a gate insulating film over the gate electrode;
• a semiconductor film over the gate insulating film;
• a buffer layer formed over the semiconductor film;
• a first insulating film formed so as to cover side surfaces of the semiconductor film and the buffer layer;
• a channel protection film over the buffer layer;
• source and drain regions on the first insulating film and the channel protection film, the source and drain regions connected to the buffer layer;
• source and drain wirings over the source and drain regions, respectively;
• a second insulating, film over the source and drain wirings;
• and
• an electrode connected to one of the source and drain wirings through a contact hole in the second insulating film,
• wherein the buffer layer is an amorphous semiconductor film, and
• wherein the source region extends beyond an end portion of the source wiring, and the drain region extends beyond an end portion of the drain wiring.

A semiconductor device having a thin film transistor comprising:

• a gate electrode over a substrate;
• a gate insulating film over the gate electrode;
• a semiconductor film over the gate insulating film;
• a buffer layer formed over the semiconductor film;
• an insulating film formed so as to cover side surfaces of the semiconductor film and the buffer layer;
• source and drain regions on the insulating film, the source and drain regions connected to the buffer layer through contact holes of the insulating film, respectively;
• and
• source and drain wirings over the source and drain regions, respectively,
• wherein the buffer layer is an amorphous semiconductor film, and
• wherein the source region extends beyond an end portion of the source wiring, and the drain region extends beyond an end portion of the drain wiring.

A semiconductor device having a thin film transistor comprising:

• a gate electrode over a substrate;
• a gate insulating film over the gate electrode;
• a semiconductor film over the gate insulating film;
• a buffer layer formed over the semiconductor film;
• a first insulating film formed so as to cover side surfaces of the semiconductor film and the buffer layer;
• source and drain regions on the first insulating film, the source and drain regions connected to the buffer layer through first contact holes of the first insulating film, respectively;
• source and drain wirings over the source and drain regions, respectively;
• a second insulating film over the source and drain wirings;
• and
• an electrode connected to one of the source and drain wirings through a second contact hole in the second insulating film,
• wherein the buffer layer is an amorphous semiconductor film, and
• wherein the source region extends beyond an end portion of the source wiring, and the drain region extends beyond an end portion of the drain wiring.