SEMICONDUCTOR DEVICE
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Abstract
Oxide layers which contain at least one metal element that is the same as that contained in an oxide semiconductor layer including a channel are formed in contact with the top surface and the bottom surface of the oxide semiconductor layer, whereby an interface state is not likely to be generated at each of an upper interface and a lower interface of the oxide semiconductor layer. Further, it is preferable that an oxide layer, which is formed using a material and a method similar to those of the oxide layers be formed over the oxide layers Accordingly, the interface state hardly influences the movement of electrons.
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Citations
13 Claims
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1. (canceled)
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2. A semiconductor device comprising:
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a first oxide layer over and in contact with an insulating surface; an oxide semiconductor layer over and in contact with the first oxide layer; a second oxide layer over and in contact with the oxide semiconductor layer; a third oxide layer over and in contact with the second oxide layer; a gate insulating layer over and in contact with the third oxide layer; and a gate electrode over and in contact with the gate insulating layer, wherein each of the first oxide layer, the oxide semiconductor layer, the second oxide layer and the third oxide layer contains indium, gallium and zinc, wherein the first oxide layer has an atomic ratio of gallium larger than an atomic ratio of indium, and wherein the third oxide layer has an atomic ratio of gallium larger than an atomic ratio of indium. - View Dependent Claims (3, 4, 5)
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6. A semiconductor device comprising:
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a first oxide layer over and in contact with an insulating surface; an oxide semiconductor layer over and in contact with the first oxide layer; a second oxide layer over and in contact with the oxide semiconductor layer; a third oxide layer over and in contact with the second oxide layer; a gate insulating layer over and in contact with the third oxide layer; and a gate electrode over and in contact with the gate insulating layer, wherein each of the first oxide layer, the oxide semiconductor layer, the second oxide layer and the third oxide layer contains indium, gallium and zinc, wherein the first oxide layer has an atomic ratio of zinc larger than an atomic ratio of indium, and wherein the third oxide layer has an atomic ratio of zinc larger than an atomic ratio of indium. - View Dependent Claims (7, 8, 9)
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10. A semiconductor device comprising:
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a first oxide layer over and in contact with an insulating surface; an oxide semiconductor layer over and in contact with the first oxide layer; a second oxide layer over and in contact with the oxide semiconductor layer; a third oxide layer over and in contact with the second oxide layer; a gate insulating layer over and in contact with the third oxide layer; and a gate electrode over and in contact with the gate insulating layer, wherein each of the first oxide layer, the oxide semiconductor layer, the second oxide layer and the third oxide layer contains indium, gallium and zinc, wherein the first oxide layer has an atomic ratio of gallium larger than an atomic ratio of indium, wherein the first oxide layer has an atomic ratio of zinc larger than an atomic ratio of indium, wherein the third oxide layer has an atomic ratio of gallium larger than an atomic ratio of indium, and wherein the third oxide layer has an atomic ratio of zinc larger than an atomic ratio of indium. - View Dependent Claims (11, 12, 13)
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Specification