Patent ID: 7635865

Claim:
A display device comprising: a substrate; a first N-channel thin film transistor formed over the substrate, the first N-channel thin film transistor comprising: a first semiconductor island including at least a first channel region, a second channel region, lightly doped regions, a capacitor forming region, and source and drain regions; a first gate insulating film formed over the first semiconductor island; a first gate electrode formed over the first channel region with the first gate insulating film interposed therebetween; and a second gate electrode formed over the second channel region with the first gate insulating film interposed therebetween; a driver circuit including at least one second N-channel type thin film transistor and a P-channel type thin film transistor formed over the substrate, the second N-channel type thin film transistor comprising: a second semiconductor island including at least a third channel region; a second gate insulating film formed over the second semiconductor island; a third gate electrode formed over the third channel region with the second gate insulating film interposed therebetween; a capacitor electrode formed over the capacitor forming region of the first semiconductor island with the first gate insulating film interposed therebetween; a protecting insulating film covering the first, second and third gate electrodes and the first and second semiconductor islands, the protecting insulating film comprising silicon nitride; and a pixel electrode formed over the protecting insulating film and electrically connected to one of the source and drain regions of the first semiconductor island, wherein each of the first, second and third gate electrodes has tapered edges with a taper angle of in a range of 20° to 70°, wherein each of the lightly doped regions is overlapped by the tapered edges of the first and second gate electrodes at least partly.