Semiconductor device including an oxide semiconductor
First Claim
1. A semiconductor device comprising:
- a first oxide semiconductor layer comprising indium and gallium;
a second oxide semiconductor layer comprising indium and gallium over the first oxide semiconductor layer;
a third oxide semiconductor layer comprising indium and gallium over the second oxide semiconductor layer;
an insulating layer over the third oxide semiconductor layer; and
a gate electrode over the insulating layer,wherein a content of the indium in the second oxide semiconductor layer is higher than a content of the gallium in the second oxide semiconductor layer,wherein a proportion of the indium to the gallium in the first oxide semiconductor layer is higher than a proportion of the indium to the gallium in the third oxide semiconductor layer, andwherein the third oxide semiconductor layer comprises a region which is not overlapped with the gate electrode and comprises at least one of nitrogen, argon, and aluminum.
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Accused Products
Abstract
A transistor having high field-effect mobility is provided. In order that an oxide semiconductor layer through which carriers flow is not in contact with a gate insulating film, a buried channel structure in which the oxide semiconductor layer through which carriers flow is separated from the gate insulating film is employed. Specifically, an oxide semiconductor layer having high conductivity is provided between two oxide semiconductor layers. Further, an impurity element is added to the oxide semiconductor layer in a self-aligned manner so that the resistance of a region in contact with an electrode layer is reduced. Further, the oxide semiconductor layer in contact with the gate insulating layer has a larger thickness than the oxide semiconductor layer having high conductivity.
369 Citations
12 Claims
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1. A semiconductor device comprising:
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a first oxide semiconductor layer comprising indium and gallium; a second oxide semiconductor layer comprising indium and gallium over the first oxide semiconductor layer; a third oxide semiconductor layer comprising indium and gallium over the second oxide semiconductor layer; an insulating layer over the third oxide semiconductor layer; and a gate electrode over the insulating layer, wherein a content of the indium in the second oxide semiconductor layer is higher than a content of the gallium in the second oxide semiconductor layer, wherein a proportion of the indium to the gallium in the first oxide semiconductor layer is higher than a proportion of the indium to the gallium in the third oxide semiconductor layer, and wherein the third oxide semiconductor layer comprises a region which is not overlapped with the gate electrode and comprises at least one of nitrogen, argon, and aluminum. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A semiconductor device comprising:
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a first oxide semiconductor layer comprising indium and gallium, the first oxide semiconductor layer comprising a channel formation region; a second oxide semiconductor layer comprising indium and gallium over the first oxide semiconductor layer; a gate insulating layer comprising silicon over the second oxide semiconductor layer; and a gate electrode over the gate insulating layer, wherein a content of the indium in the first oxide semiconductor layer is higher than a content of the gallium in the first oxide semiconductor layer, and wherein the second oxide semiconductor layer comprises a region which is not overlapped with the gate electrode and comprises at least one of nitrogen, argon, and aluminum. - View Dependent Claims (9, 10, 11, 12)
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Specification