Metal oxide semiconductor transistors having a polysilicon gate electrode with nonuniform doping in source-drain direction
First Claim
1. A metal insulator thin-film-polysilicon semiconductor transistor structure comprising:
- (a) source and drain regions located in the thin-film-polysilicon semiconductor and spaced apart by an intermediate region, located in the thin-film-polysilicon semiconductor, of length L, the intermediate region and the source and drain regions forming a thin-film polysilicon structure,(b) the insulator located on the intermediate region,(c) a polycrystalline semiconductor gate electrode layer located on the insulator and consisting essentially of first and second contiguous gate electrode regions,(d) an insulating substrate having a top major surface contiguous with a bottom major surface of the intermediate region and with the source and drain regions,the first gate electrode region, having a first average impurity doping concentration, extending from a first location overlying an edge of the source region to an edge of the second gate electrode region,the second gate electrode region, having a second average impurity doping concentration, extending from the edge of the second gate electrode region to a second location overlying an edge of the drain region,the ratio of the first to the second average impurity doping concentration being equal to at least 10, and the first gate electrode region having a conductivity type opposite to that of the source drain.
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Accused Products
Abstract
The gate electrode of a polysilicon gate MOS transistor--the transistor having either a thin film polysilicon substrate or a bulk monocrystalline substrate--has a pair of contiguous regions: a heavily doped gate electrode region near the source, and a lightly doped gate electrode region near the drain. The gate electrode region near the drain is thus doped significantly more lightly, in order to reduce electric fields in the channel region in the neighborhood of the drain (and hence reduce field induced leakage currents) when voltages are applied to turn transistor OFF. At the same time, sufficient impurity doping is introduced into the gate electrode region near the source in order to enable the transistor to turn ON when other suitable voltages are applied.
46 Citations
14 Claims
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1. A metal insulator thin-film-polysilicon semiconductor transistor structure comprising:
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(a) source and drain regions located in the thin-film-polysilicon semiconductor and spaced apart by an intermediate region, located in the thin-film-polysilicon semiconductor, of length L, the intermediate region and the source and drain regions forming a thin-film polysilicon structure, (b) the insulator located on the intermediate region, (c) a polycrystalline semiconductor gate electrode layer located on the insulator and consisting essentially of first and second contiguous gate electrode regions, (d) an insulating substrate having a top major surface contiguous with a bottom major surface of the intermediate region and with the source and drain regions, the first gate electrode region, having a first average impurity doping concentration, extending from a first location overlying an edge of the source region to an edge of the second gate electrode region, the second gate electrode region, having a second average impurity doping concentration, extending from the edge of the second gate electrode region to a second location overlying an edge of the drain region, the ratio of the first to the second average impurity doping concentration being equal to at least 10, and the first gate electrode region having a conductivity type opposite to that of the source drain. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification