Semiconductor device including an oxide semiconductor
AssigneeSemiconductor Energy Laboratory Co., Ltd.
InventorShunpei Yamazaki
Life of this patent
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Abstract
High field-effect mobility is provided for a transistor including an oxide semiconductor. Further, a highly reliable semiconductor device including the transistor is provided. In a bottom-gate transistor including an oxide semiconductor layer, an oxide semiconductor layer functioning as a current path (channel) of the transistor is sandwiched between oxide semiconductor layers having lower carrier densities than the oxide semiconductor layer. In such a structure, the channel is formed away from the interface of the oxide semiconductor stacked layer with an insulating layer in contact with the oxide semiconductor stacked layer, i.e., a buried channel is formed.
Claims12
A semiconductor device comprising:
- a transistor;
- and
- a photodiode electrically connected to the transistor;
- wherein the transistor comprises:
- a first oxide semiconductor layer;
- a second oxide semiconductor layer over and in direct contact with the first oxide semiconductor layer;
- a third oxide semiconductor layer in direct contact with a top surface of the second oxide semiconductor layer;
- a gate electrode layer overlapping with the second oxide semiconductor layer with an insulating layer interposed therebetween;
- and
- a source electrode layer and a drain electrode layer electrically connected to the second oxide semiconductor layer,
- wherein a difference between a Fermi level and a bottom of a conduction band in the second oxide semiconductor layer is smaller than those in the first oxide semiconductor layer and the third oxide semiconductor layer.
A semiconductor device comprising:
- a transistor;
- and
- a photodiode electrically connected to the transistor;
- wherein the transistor comprises:
- a first oxide semiconductor layer;
- a second oxide semiconductor layer on and in direct contact with the first oxide semiconductor layer;
- a third oxide semiconductor layer in direct contact with a top surface of the second oxide semiconductor layer;
- a gate electrode layer overlapping with the second oxide semiconductor layer with an insulating layer interposed therebetween;
- and
- a source electrode layer and a drain electrode layer electrically connected to the second oxide semiconductor layer,
- wherein a difference between a Fermi level and a bottom of a conduction band in the second oxide semiconductor layer is smaller than those in the first oxide semiconductor layer and the third oxide semiconductor layer, and
- wherein the photodiode comprises an amorphous silicon film.
Dependencies are inferred from the claim text.