Semiconductor device and method for manufacturing semiconductor device
First Claim
1. A semiconductor device comprising:
- a substrate having an insulating surface;
a source electrode layer and a drain electrode layer over the substrate;
a first oxide semiconductor layer over the source electrode layer and the drain electrode layer;
a second oxide semiconductor layer over the first oxide semiconductor layer;
a gate insulating layer over the second oxide semiconductor layer; and
a gate electrode layer overlapping with the oxide semiconductor layer with the gate insulating layer interposed therebetween,wherein the first oxide semiconductor layer comprises a stack of a first oxide semiconductor film and a second oxide semiconductor film,wherein the first oxide semiconductor film and the second oxide semiconductor film each include crystals,wherein an energy gap of the first oxide semiconductor film is different from an energy gap of the second oxide semiconductor film, andwherein the second oxide semiconductor layer covers and is in contact with side surfaces of the first oxide semiconductor film and side surfaces of the second oxide semiconductor film.
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Accused Products
Abstract
A transistor which is formed using an oxide semiconductor layer and has electric characteristics needed for the intended use, and a semiconductor device including the transistor are provided. The transistor is formed using an oxide semiconductor stack including at least a first oxide semiconductor layer in contact with a source electrode layer and a drain electrode layer and a second oxide semiconductor layer which is provided over the first oxide semiconductor layer and has an energy gap different from that of the first oxide semiconductor layer. There is no limitation on the stacking order of the first oxide semiconductor layer and the second oxide semiconductor layer as long as their energy gaps are different from each other.
177 Citations
24 Claims
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1. A semiconductor device comprising:
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a substrate having an insulating surface; a source electrode layer and a drain electrode layer over the substrate; a first oxide semiconductor layer over the source electrode layer and the drain electrode layer; a second oxide semiconductor layer over the first oxide semiconductor layer; a gate insulating layer over the second oxide semiconductor layer; and a gate electrode layer overlapping with the oxide semiconductor layer with the gate insulating layer interposed therebetween, wherein the first oxide semiconductor layer comprises a stack of a first oxide semiconductor film and a second oxide semiconductor film, wherein the first oxide semiconductor film and the second oxide semiconductor film each include crystals, wherein an energy gap of the first oxide semiconductor film is different from an energy gap of the second oxide semiconductor film, and wherein the second oxide semiconductor layer covers and is in contact with side surfaces of the first oxide semiconductor film and side surfaces of the second oxide semiconductor film. - View Dependent Claims (2, 3, 4)
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5. A semiconductor device comprising:
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a substrate having an insulating surface; a source electrode layer and a drain electrode layer formed over the substrate; a first oxide semiconductor layer over the source electrode layer and the drain electrode layer; a second oxide semiconductor layer over the first oxide semiconductor layer; a gate insulating layer over the second oxide semiconductor layer; and a gate electrode layer overlapping with the second oxide semiconductor layer with the gate insulating layer interposed therebetween, wherein the first oxide semiconductor layer comprises a stack of a first oxide semiconductor film and a second oxide semiconductor film, wherein an energy gap of the first oxide semiconductor film is different from an energy gap of the second oxide semiconductor film, and wherein the second oxide semiconductor layer covers and is in contact with side surfaces of the first oxide semiconductor film and side surfaces of the second oxide semiconductor film. - View Dependent Claims (6, 7, 8, 9, 10, 14)
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11. A method for manufacturing a semiconductor device, comprising the steps of:
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forming a source electrode layer and a drain electrode layer over an oxide insulating film; forming a first oxide semiconductor layer over the source electrode layer and the drain electrode layer; forming a second oxide semiconductor layer over the first oxide semiconductor layer; forming a gate insulating layer over the source electrode layer, the drain electrode layer, and the second oxide semiconductor layer; and forming a gate electrode layer overlapping with the first oxide semiconductor layer and the second oxide semiconductor layer with the gate insulating layer interposed therebetween, wherein the first oxide semiconductor layer comprises a stack of a first oxide semiconductor film and a second oxide semiconductor film, wherein the first oxide semiconductor film and the second oxide semiconductor film each include crystals, wherein an energy gap of the first oxide semiconductor film is different from an energy gap of the second oxide semiconductor film, and wherein the second oxide semiconductor layer is in contact with side surfaces of the first oxide semiconductor film and side surfaces of the second oxide semiconductor film. - View Dependent Claims (12, 13, 15)
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16. A semiconductor device comprising:
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a substrate; a first oxide semiconductor film over the substrate; a second oxide semiconductor film over the first oxide semiconductor film; a third oxide semiconductor film over the second oxide semiconductor film; a gate insulating layer over the third oxide semiconductor film; and a gate electrode layer overlapping with at least the second oxide semiconductor film with the gate insulating layer interposed therebetween, wherein an energy gap of the first oxide semiconductor film is different from an energy gap of the second oxide semiconductor film, and wherein the third oxide semiconductor film covers and is in contact with side surfaces of the first oxide semiconductor film and side surfaces of the second oxide semiconductor film. - View Dependent Claims (17, 18, 19, 20)
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21. A method for manufacturing a semiconductor device, comprising the steps of:
- forming a first oxide semiconductor layer and a second oxide semiconductor layer over a substrate, wherein the second oxide semiconductor layer is provided over the first oxide semiconductor layer;
forming an oxide semiconductor film over the second oxide semiconductor layer so as to cover and be in contact with side surfaces of the first oxide semiconductor layer and side surfaces of the second oxide semiconductor layer;
processing the oxide semiconductor film to form a third oxide semiconductor layer which covers and is in contact with the side surfaces of the first oxide semiconductor layer and the side surfaces of the second oxide semiconductor layer;
forming a gate insulating layer over the third oxide semiconductor layer; and
forming a gate electrode layer overlapping with at least the second oxide semiconductor layer with the gate insulating layer interposed therebetween, and wherein an energy gap of the first oxide semiconductor layer is different from an energy gap of the second oxide semiconductor layer. - View Dependent Claims (22, 23, 24)
- forming a first oxide semiconductor layer and a second oxide semiconductor layer over a substrate, wherein the second oxide semiconductor layer is provided over the first oxide semiconductor layer;
Specification