SEMICONDUCTOR DEVICE AND METHOD FOR MANUFACTURING THE SAME
First Claim
1. A semiconductor device comprising a transistor, the transistor comprising:
- a first oxide semiconductor layer;
a second oxide semiconductor layer over the first oxide semiconductor layer;
a source electrode over the second oxide semiconductor layer; and
a drain electrode over the second oxide semiconductor layer,wherein the first oxide semiconductor layer includes a channel formation region,wherein the second oxide semiconductor layer includes a first region overlapping with the channel formation region,wherein the second oxide semiconductor layer includes a second region in contact with the source electrode,wherein the second oxide semiconductor layer includes a third region in contact with the drain electrode,wherein the first region is located between the source electrode and the drain electrode,wherein a thickness of each of the second region and the third region is thicker than a thickness of the first region,wherein the first region has a first electrical conductivity,wherein the second region has a second electrical conductivity,wherein the third region has a third electrical conductivity, andwherein each of the second electrical conductivity and the third electrical conductivity is higher than the first electrical conductivity.
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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.
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Citations
20 Claims
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1. A semiconductor device comprising a transistor, the transistor comprising:
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a first oxide semiconductor layer; a second oxide semiconductor layer over the first oxide semiconductor layer; a source electrode over the second oxide semiconductor layer; and a drain electrode over the second oxide semiconductor layer, wherein the first oxide semiconductor layer includes a channel formation region, wherein the second oxide semiconductor layer includes a first region overlapping with the channel formation region, wherein the second oxide semiconductor layer includes a second region in contact with the source electrode, wherein the second oxide semiconductor layer includes a third region in contact with the drain electrode, wherein the first region is located between the source electrode and the drain electrode, wherein a thickness of each of the second region and the third region is thicker than a thickness of the first region, wherein the first region has a first electrical conductivity, wherein the second region has a second electrical conductivity, wherein the third region has a third electrical conductivity, and wherein each of the second electrical conductivity and the third electrical conductivity is higher than the first electrical conductivity. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A semiconductor device comprising a transistor, the transistor comprising:
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a first oxide semiconductor layer; a second oxide semiconductor layer over the first oxide semiconductor layer; a source electrode over the second oxide semiconductor layer; and a drain electrode over the second oxide semiconductor layer, wherein the first oxide semiconductor layer includes a channel formation region, wherein the second oxide semiconductor layer includes a first region overlapping with the channel formation region, wherein the second oxide semiconductor layer includes a second region in contact with the source electrode, wherein the second oxide semiconductor layer includes a third region in contact with the drain electrode, wherein the first region is located between the source electrode and the drain electrode, wherein a thickness of each of the second region and the third region is thicker than a thickness of the first region, wherein the first region has a first electrical conductivity, wherein the second region has a second electrical conductivity, wherein the third region has a third electrical conductivity, wherein each of the second electrical conductivity and the third electrical conductivity is higher than the first electrical conductivity, and wherein the first region contains oxygen at a higher concentration than the second region and the third region. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification