Patent ID: 8324693

Claim:
A semiconductor device comprising: a pixel portion comprising a first thin film transistor over a substrate; and a driver circuit comprising a second thin film transistor over the substrate, wherein at least one of the first thin film transistor and the second thin film transistor comprises: a semiconductor layer on an insulating surface over the substrate, the semiconductor layer comprising a source region, a drain region, and a channel region located between the source region and the drain region; a gate electrode over 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, the impurity region being provided between the channel region and at least one of the source region and the drain region; an insulating layer comprising silicon nitride over the gate electrode and the semiconductor layer, the insulating layer including a portion in contact with the gate insulating layer; and a pixel electrode over the insulating layer, wherein the gate insulating layer includes 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 the pixel electrode.