SEMICONDUCTOR DEVICE AND METHOD FOR MANUFACTURING THE SAME
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Abstract
It is an object to provide a highly reliable semiconductor device including a thin film transistor with stable electric characteristics. In a semiconductor device including an inverted staggered thin film transistor whose semiconductor layer is an oxide semiconductor layer, a buffer layer is provided over the oxide semiconductor layer. The buffer layer is in contact with a channel formation region of the semiconductor layer and source and drain electrode layers. A film of the buffer layer has resistance distribution. A region provided over the channel formation region of the semiconductor layer has lower electrical conductivity than the channel formation region of the semiconductor layer, and a region in contact with the source and drain electrode layers has higher electrical conductivity than the channel formation region of the semiconductor layer.
1 Citation
19 Claims
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1. (canceled)
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2. A semiconductor device comprising:
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a gate electrode over a substrate; a gate insulating layer over the gate electrode; a first oxide semiconductor layer over the gate insulating layer; a second oxide semiconductor layer over the first oxide semiconductor layer; a source electrode electrically connected to the second oxide semiconductor layer; a drain electrode electrically connected to the second oxide semiconductor layer; a first region between the second oxide semiconductor layer and the source electrode; and a second region between the second oxide semiconductor layer and the drain electrode, wherein each of the first oxide semiconductor layer and the second oxide semiconductor layer comprises indium, gallium and zinc, wherein a composition ratio of the first region is different from a composition ratio of each of the first oxide semiconductor layer and the second oxide semiconductor layer, wherein a composition ratio of the second region is different from a composition ratio of each of the first oxide semiconductor layer and the second oxide semiconductor layer, wherein each of the source electrode and the drain electrode comprises at least one of titanium, aluminum, manganese, magnesium, zirconium, beryllium, thorium, and copper, and wherein each of the source electrode and the drain electrode is in contact with the gate insulating layer. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10)
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11. A semiconductor device comprising:
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a gate electrode over a substrate; a gate insulating layer over the gate electrode; a first oxide semiconductor layer over the gate insulating layer; a second oxide semiconductor layer over the first oxide semiconductor layer; a source electrode electrically connected to the second oxide semiconductor layer; a drain electrode electrically connected to the second oxide semiconductor layer; a first region between the second oxide semiconductor layer and the source electrode; and a second region between the second oxide semiconductor layer and the drain electrode, wherein each of the first oxide semiconductor layer and the second oxide semiconductor layer comprises indium, gallium and zinc, wherein a composition ratio of the first region is different from a composition ratio of each of the first oxide semiconductor layer and the second oxide semiconductor layer, wherein a composition ratio of the second region is different from the composition ratio of each of the first oxide semiconductor layer and the second oxide semiconductor layer, wherein each of the source electrode and the drain electrode comprises at least one of titanium, aluminum, manganese, magnesium, zirconium, beryllium, thorium, and copper, wherein each of the source electrode and the drain electrode is in contact with the gate insulating layer, and wherein an upper edge of the first oxide semiconductor layer is aligned with a bottom edge of the second oxide semiconductor layer. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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Specification