Method of fabricating a semiconductor device

摘要

There is provided a thin film transistor having improved reliability. A gate electrode includes a first gate electrode having a taper portion and a second gate electrode with a width narrower than the first gate electrode. A semiconductor layer is doped with phosphorus of a low concentration through the first gate electrode. In the semiconductor layer, two kinds of n−-type impurity regions are formed between a channel formation region and n+-type impurity regions. Some of the n−-type impurity regions overlap with a gate electrode, and the other n−-type impurity regions do not overlap with the gate electrode. Since the two kinds of n−-type impurity regions are formed, an off current can be reduced, and deterioration of characteristics can be suppressed.

主权项

1. A display device comprising:
a substrate; a first transistor over the substrate, the first transistor comprising a semiconductor layer formed on an insulating surface and a gate electrode over the semiconductor layer, the semiconductor layer comprising a channel formation region comprising polycrystalline silicon; a driving circuit comprising a second transistor over the substrate, the second transistor comprising a semiconductor layer formed on the insulating surface; a first insulating film over the first transistor and the second transistor; a pixel electrode over the first insulating film and electrically connected to the first transistor; a light emitting layer over the pixel electrode, the light emitting layer comprising an organic compound; a second electrode over the pixel electrode so that the light emitting layer is disposed between the pixel electrode and the second electrode; a covering material over the second electrode; a first sealing material interposed between the substrate and the covering material, wherein the first sealing material is disposed along peripheries of the substrate and the covering material; and a second sealing material outside of and along the first sealing material, wherein the second sealing material is in contact with a side surface of the covering material.