Semiconductor device and method for manufacturing the same
First Claim
1. A method for manufacturing a semiconductor device comprising the steps of:
- forming a gate electrode layer over a substrate;
forming a gate insulating layer over the gate electrode layer;
forming a conductive film over the gate insulating layer;
etching the conductive film to form source and drain electrode layers;
forming a first oxide semiconductor film over the gate insulating layer and the source and drain electrode layers by a sputtering method;
forming a second oxide semiconductor film over the first oxide semiconductor film by a sputtering method; and
etching the first oxide semiconductor film and the second oxide semiconductor film to form an oxide semiconductor layer and a semiconductor layer,wherein the oxide semiconductor layer is provided to be in contact with the gate insulating layer and side face portions of the source and drain electrode layers,wherein the semiconductor layer is provided over the oxide semiconductor layer, andwherein a proportion of a flow rate of an oxygen gas to the whole film-formation gas for forming the second oxide semiconductor film is made lower than a proportion of a flow rate of an oxygen gas to the whole film-formation gas for forming the first oxide semiconductor film.
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Abstract
An object is to increase field effect mobility of a thin film transistor including an oxide semiconductor. Another object is to stabilize electrical characteristics of the thin film transistor. In a thin film transistor including an oxide semiconductor layer, a semiconductor layer or a conductive layer having higher electrical conductivity than the oxide semiconductor is formed over the oxide semiconductor layer, whereby field effect mobility of the thin film transistor can be increased. Further, by forming a semiconductor layer or a conductive layer having higher electrical conductivity than the oxide semiconductor between the oxide semiconductor layer and a protective insulating layer of the thin film transistor, change in composition or deterioration in film quality of the oxide semiconductor layer is prevented, so that electrical characteristics of the thin film transistor can be stabilized.
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Citations
26 Claims
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1. A method for manufacturing a semiconductor device comprising the steps of:
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forming a gate electrode layer over a substrate; forming a gate insulating layer over the gate electrode layer; forming a conductive film over the gate insulating layer; etching the conductive film to form source and drain electrode layers; forming a first oxide semiconductor film over the gate insulating layer and the source and drain electrode layers by a sputtering method; forming a second oxide semiconductor film over the first oxide semiconductor film by a sputtering method; and etching the first oxide semiconductor film and the second oxide semiconductor film to form an oxide semiconductor layer and a semiconductor layer, wherein the oxide semiconductor layer is provided to be in contact with the gate insulating layer and side face portions of the source and drain electrode layers, wherein the semiconductor layer is provided over the oxide semiconductor layer, and wherein a proportion of a flow rate of an oxygen gas to the whole film-formation gas for forming the second oxide semiconductor film is made lower than a proportion of a flow rate of an oxygen gas to the whole film-formation gas for forming the first oxide semiconductor film. - View Dependent Claims (2, 3, 4, 5, 12, 13, 14)
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6. A method for manufacturing a semiconductor device comprising the steps of:
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forming a gate electrode layer over a substrate; forming a gate insulating layer over the gate electrode layer; forming a conductive film over the gate insulating layer; etching the conductive film to form source and drain electrode layers; forming an oxide semiconductor layer over the gate insulating layer and the source and drain electrode layers; and forming a semiconductor layer over the oxide semiconductor layer, wherein the oxide semiconductor layer is provided to be in contact with the gate insulating layer and side face portions of the source and drain electrode layers, and wherein electrical conductivity of the semiconductor layer is higher than electrical conductivity of the oxide semiconductor layer. - View Dependent Claims (7, 8, 9, 10, 11, 15, 16, 17)
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18. A method for manufacturing a semiconductor device, comprising the steps of:
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forming a gate electrode layer over a substrate; forming a gate insulating layer over the gate electrode layer; forming a conductive film over the gate insulating layer; etching the conductive film to form source and drain electrode layers; forming an oxide semiconductor layer over the gate insulating layer and the source and drain electrode layers; forming a semiconductor layer over the oxide semiconductor layer; performing a heat treatment after forming the oxide semiconductor layer; and forming a protective film over the semiconductor layer, wherein the oxide semiconductor layer is provided to be in contact with the gate insulating layer and side face portions of the source and drain electrode layers, and wherein electrical conductivity of the semiconductor layer is higher than electrical conductivity of the oxide semiconductor layer. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26)
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Specification