Semiconductor device and manufacturing method thereof
First Claim
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1. A semiconductor device comprising:
- an oxide semiconductor stacked layer comprising a first oxide semiconductor layer, a second oxide semiconductor layer over the first oxide semiconductor layer, and a third oxide semiconductor layer over the second oxide semiconductor layer;
a gate electrode layer and the oxide semiconductor stacked layer overlap each other; and
a gate insulating film between the gate electrode layer and the oxide semiconductor stacked layer,wherein energy at a bottom of a conduction band of the second oxide semiconductor layer is lower than energy at a bottom of a conduction band of the first oxide semiconductor layer and energy at a bottom of a conduction band of the third oxide semiconductor layer, andwherein the second oxide semiconductor layer comprises a crystal including a c-axis alignment.
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Abstract
Provided are a transistor which has electrical characteristics requisite for its purpose and uses an oxide semiconductor layer and a semiconductor device including the transistor. In the bottom-gate transistor in which at least a gate electrode layer, a gate insulating film, and the semiconductor layer are stacked in this order, an oxide semiconductor stacked layer including at least two oxide semiconductor layers whose energy gaps are different from each other is used as the semiconductor layer. Oxygen and/or a dopant may be added to the oxide semiconductor stacked layer.
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Citations
24 Claims
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1. A semiconductor device comprising:
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an oxide semiconductor stacked layer comprising a first oxide semiconductor layer, a second oxide semiconductor layer over the first oxide semiconductor layer, and a third oxide semiconductor layer over the second oxide semiconductor layer; a gate electrode layer and the oxide semiconductor stacked layer overlap each other; and a gate insulating film between the gate electrode layer and the oxide semiconductor stacked layer, wherein energy at a bottom of a conduction band of the second oxide semiconductor layer is lower than energy at a bottom of a conduction band of the first oxide semiconductor layer and energy at a bottom of a conduction band of the third oxide semiconductor layer, and wherein the second oxide semiconductor layer comprises a crystal including a c-axis alignment. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A semiconductor device comprising:
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an oxide semiconductor stacked layer comprising a first oxide semiconductor layer, a second oxide semiconductor layer over the first oxide semiconductor layer, and a third oxide semiconductor layer over the second oxide semiconductor layer; a gate electrode layer and the oxide semiconductor stacked layer overlap each other; and a gate insulating film between the gate electrode layer and the oxide semiconductor stacked layer, wherein energy at a bottom of a conduction band of the second oxide semiconductor layer is lower than energy at a bottom of a conduction band of the first oxide semiconductor layer and energy at a bottom of a conduction band of the third oxide semiconductor layer, wherein the oxide semiconductor stacked layer comprises a channel formation region, and wherein the channel formation region comprises a crystal including a c-axis alignment. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A semiconductor device comprising:
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a first oxide semiconductor layer; a second oxide semiconductor layer on the first oxide semiconductor layer; a third oxide semiconductor layer on the second oxide semiconductor layer, wherein the third oxide semiconductor layer covers side surfaces of the second oxide semiconductor layer; a source electrode on and in contact with the third oxide semiconductor layer; a drain electrode on and in contact with the third oxide semiconductor layer; a gate electrode layer comprising a region overlapping with the first oxide semiconductor layer, the second oxide semiconductor layer and the third oxide semiconductor layer; wherein energy at a bottom of a conduction band of the second oxide semiconductor layer is lower than energy at a bottom of a conduction band of the first oxide semiconductor layer and energy at a bottom of a conduction band of the third oxide semiconductor layer, and wherein the second oxide semiconductor layer comprises a crystal including a c-axis alignment. - View Dependent Claims (21, 22, 23, 24)
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Specification