Patent ID: 6909114

Claim:
A semiconductor device having an active matrix display device, said display device comprising: a first thin film transistor formed over an insulating surface; a pixel electrode electrically connected to said first thin film transistor; a driver circuit including a second thin film transistor formed over said insulating surface for driving said first thin film transistor, wherein said first thin film transistor comprises: a first semiconductor island over the insulating surface; source and drain regions formed in the semiconductor island; a first channel forming region in the first semiconductor island between the source and drain regions; a pair of lightly doped regions formed between the first channel forming region and the source and drain regions, wherein an impurity concentration in the lightly doped regions is smaller than that in the source and drain regions; a gate electrode formed over the semiconductor island with a gate insulating film Interposed therebetween; an insulating film formed over the gate electrode and the gate insulating film; wherein said gate electrode comprises at least a first conductive layer and a second conductive layer formed on the first conductive layer, said first conductive layer having a pair of tapered portions which extend beyond side edges of the second conductive layer, wherein the pair of lightly doped regions has a pair of first portions which are overlapped by the pair of tapered portions of the first conductive layer, and a pair of second portions which extend beyond side edges of the first conductive layer, and wherein said insulating film is in direct contact with at least side surfaces and a top surface of the second conductive layer.