Semiconductor device and method for manufacturing the same
First Claim
1. A semiconductor device comprising:
- a first oxide layer over and in contact with an insulating surface;
a second oxide layer over and in contact with the first oxide layer;
a third oxide layer over and in contact with the second oxide layer;
an insulating layer over and in contact with the third oxide layer; and
a gate electrode over and in contact with the insulating layer,wherein each of the first oxide layer, the second oxide layer and the third oxide layer contains indium, gallium and zinc,wherein a thickness of the second oxide layer is larger than a thickness of the first oxide layer; and
wherein each of the first oxide layer and the third oxide layer has an atomic ratio of zinc larger than an atomic ratio of indium, and an atomic ratio of gallium larger than the atomic ratio of zinc.
1 Assignment
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Accused Products
Abstract
The reliability of a semiconductor device is increased by suppression of a variation in electric characteristics of a transistor as much as possible. As a cause of a variation in electric characteristics of a transistor including an oxide semiconductor, the concentration of hydrogen in the oxide semiconductor, the density of oxygen vacancies in the oxide semiconductor, or the like can be given. A source electrode and a drain electrode are formed using a conductive material which is easily bonded to oxygen. A channel formation region is formed using an oxide layer formed by a sputtering method or the like under an atmosphere containing oxygen. Thus, the concentration of hydrogen in a stack, in particular, the concentration of hydrogen in a channel formation region can be reduced.
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Citations
10 Claims
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1. A semiconductor device comprising:
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a first oxide layer over and in contact with an insulating surface; a second oxide layer over and in contact with the first oxide layer; a third oxide layer over and in contact with the second oxide layer; an insulating layer over and in contact with the third oxide layer; and a gate electrode over and in contact with the insulating layer, wherein each of the first oxide layer, the second oxide layer and the third oxide layer contains indium, gallium and zinc, wherein a thickness of the second oxide layer is larger than a thickness of the first oxide layer; and wherein each of the first oxide layer and the third oxide layer has an atomic ratio of zinc larger than an atomic ratio of indium, and an atomic ratio of gallium larger than the atomic ratio of zinc. - View Dependent Claims (2, 3, 4)
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5. A semiconductor device comprising:
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a first oxide layer over and in contact with an insulating surface; a second oxide layer over and in contact with the first oxide layer; a third oxide layer over and in contact with the second oxide layer; an insulating layer over and in contact with the third oxide layer; and a gate electrode over and in contact with the insulating layer, wherein each of the first oxide layer, the second oxide layer and the third oxide layer contains indium, gallium and zinc, wherein each of the first oxide layer and the third oxide layer has an atomic ratio of zinc larger than an atomic ratio of indium, and an atomic ratio of gallium larger than the atomic ratio of zinc, and wherein the second oxide layer has an atomic ratio of indium larger than an atomic ratio of gallium and an atomic ratio of zinc. - View Dependent Claims (6, 7, 8)
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9. A semiconductor device comprising:
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a first oxide layer comprising In, Ga and Zn; a second oxide layer over and in contact with the first oxide layer, the second oxide layer being formed by an oxide target (In;
Ga;
Zn=1;
6;
4); anda gate electrode that overlaps with the first oxide layer and the second oxide layer. - View Dependent Claims (10)
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Specification