Method of fabricating a semiconductor device
AssigneeSemiconductor Energy Laboratory Co., Ltd.
InventorShunpei Yamazaki
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Abstract
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.
Claims5
(canceled)
A semiconductor element having a top gate type LDD structure located on a substrate, comprising:
- an upper gate electrode;
- a lower gate electrode, at least a side thereof on the source electrode side and the drain electrode side protruding from said upper gate electrode, and located in close contact with said upper gate electrode;
- and
- a semiconductor section having a channel area directly below said upper gate electrode and said lower gate electrode, an LDD area directly below a protruding portion of said lower electrode, and a source area and a drain area not covered with said upper gate electrode and said lower electrode;
- said lower gate electrode comprises a low resistance metal material;
- and
- said upper gate electrode comprises a high-density metal material or a hydrogen adsorptive metal, and has a high masking ability of hydrogen ions injected during injection of impurities.
Gate type semiconductor element located on a substrate, having gate electrodes comprising an upper gate electrode and a lower gate electrode located one on top of the other in close contact with each other on a gate insulating film, wherein:
- said lower gate electrode comprises a low-resistance metal material;
- and
- said upper gate electrode comprises a high-density metal material or a hydrogen adsorptive metal, and a high-masking electrode having a high masking ability of hydrogen ions injected during injection of impurities.
Dependencies are inferred from the claim text.