Patent ID: 7301209

Claim:
A semiconductor device comprising: a pixel portion comprising a first thin film transistor; and a driver circuit comprising a second thin film transistor, wherein each of the first thin film transistor and the second thin film transistor comprising: a silicon island over a substrate having an insulating surface, the silicon island comprising a source region, a drain region, and a channel region located between the source region and the drain region; a gate electrode provided adjacent to the channel region with a gate insulating layer interposed therebetween; an impurity region having a lower concentration of an impurity than concentrations of the impurity in the source region and the drain region provided between the channel region and at least one of the source region and the drain region; a layer comprising silicon nitride over the gate electrode and the silicon island, the layer having a portion in contact with the gate insulating layer; wherein the gate insulating layer has a first portion over the channel region and a second portion over the impurity region, at least a portion of the second portion is thinner than the first portion, wherein one of the source region and the drain region of the first thin film transistor is electrically connected to a pixel electrode, and wherein the pixel electrode is formed over the layer comprising silicon nitride.