Semiconductor device
First Claim
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1. A semiconductor device comprising:
- a first gate electrode layer over an insulating surface;
a first insulating layer over the first gate electrode layer;
oxide semiconductor stacked layers comprising a first oxide semiconductor layer and a second oxide semiconductor layer and overlapping with the first gate electrode layer with the first insulating layer interposed between the first gate electrode layer and the oxide semiconductor stacked layers;
a source electrode layer and a drain electrode layer over and in contact with the second oxide semiconductor layer;
a second insulating layer over and in contact with the source electrode layer, the drain electrode layer, and an upper surface of the second oxide semiconductor layer between the source electrode layer and the drain electrode layer; and
a second gate electrode layer overlapping with the oxide semiconductor stacked layers with the second insulating layer interposed between the second gate electrode layer and the oxide semiconductor stacked layers,wherein a region of the second oxide semiconductor layer in contact with the second insulating layer has a smaller thickness than a region of the second oxide semiconductor layer in contact with the source electrode layer and a region of the second oxide semiconductor layer in contact with the drain electrode layer.
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Abstract
A transistor includes oxide semiconductor stacked layers between a first gate electrode layer and a second gate electrode layer through an insulating layer interposed between the first gate electrode layer and the oxide semiconductor stacked layers and an insulating layer interposed between the second gate electrode layer and the oxide semiconductor stacked layers. The thickness of a channel formation region is smaller than the other regions in the oxide semiconductor stacked layers. Further in this transistor, one of the gate electrode layers is provided as what is called a back gate for controlling the threshold voltage. Controlling the potential applied to the back gate enables control of the threshold voltage of the transistor, which makes it easy to maintain the normally-off characteristics of the transistor.
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Citations
16 Claims
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1. A semiconductor device comprising:
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a first gate electrode layer over an insulating surface; a first insulating layer over the first gate electrode layer; oxide semiconductor stacked layers comprising a first oxide semiconductor layer and a second oxide semiconductor layer and overlapping with the first gate electrode layer with the first insulating layer interposed between the first gate electrode layer and the oxide semiconductor stacked layers; a source electrode layer and a drain electrode layer over and in contact with the second oxide semiconductor layer; a second insulating layer over and in contact with the source electrode layer, the drain electrode layer, and an upper surface of the second oxide semiconductor layer between the source electrode layer and the drain electrode layer; and a second gate electrode layer overlapping with the oxide semiconductor stacked layers with the second insulating layer interposed between the second gate electrode layer and the oxide semiconductor stacked layers, wherein a region of the second oxide semiconductor layer in contact with the second insulating layer has a smaller thickness than a region of the second oxide semiconductor layer in contact with the source electrode layer and a region of the second oxide semiconductor layer in contact with the drain electrode layer. - View Dependent Claims (2, 3, 4, 5, 11, 13, 15)
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6. A semiconductor device comprising:
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a first gate electrode layer over an insulating surface; a first insulating layer over the first gate electrode layer; oxide semiconductor stacked layers comprising a first oxide semiconductor layer and a second oxide semiconductor layer and overlapping with the first gate electrode layer with the first insulating layer interposed between the first gate electrode layer and the oxide semiconductor stacked layers; a source electrode layer and a drain electrode layer over and in contact with the second oxide semiconductor layer; a second insulating layer over and in contact with the source electrode layer, the drain electrode layer, and an upper surface of the second oxide semiconductor layer between the source electrode layer and the drain electrode layer; and a second gate electrode layer overlapping with the oxide semiconductor stacked layers with the second insulating layer interposed between the second gate electrode layer and the oxide semiconductor stacked layers, wherein the first oxide semiconductor layer and the second oxide semiconductor layer have same constituent elements and different compositions of the constituent elements; and wherein a region of the second oxide semiconductor layer in contact with the second insulating layer has a smaller thickness than a region of the second oxide semiconductor layer in contact with the source electrode layer and a region of the second oxide semiconductor layer in contact with the drain electrode layer. - View Dependent Claims (7, 8, 9, 10, 12, 14, 16)
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Current AssigneeSemiconductor Energy Laboratory Co., Ltd.
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Original AssigneeSemiconductor Energy Laboratory Co., Ltd.
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InventorsYamazaki, Shunpei, Matsubayashi, Daisuke, Murayama, Keisuke
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Primary Examiner(s)Loke, Steven
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Assistant Examiner(s)MAZUMDER, DIDARUL A
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Application NumberUS13/860,792Publication NumberTime in Patent Office663 DaysField of Search257/43US Class Current257/43CPC Class CodesH01L 29/7831 with multiple gate structur...H01L 29/7869 having a semiconductor body...
