Thin film transistor, semiconductor device and electronic device
First Claim
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1. A thin film transistor comprising:
- a gate electrode over a substrate having an insulating surface;
a gate insulating layer which covers the gate electrode;
a first semiconductor layer which is in contact with the gate insulating layer;
a second semiconductor layer which is stacked over the first semiconductor layer; and
impurity semiconductor layers forming a source region and a drain region which are in contact with part of the second semiconductor layer,wherein the second semiconductor layer comprises an amorphous semiconductor layer having an NH group or an NH2 group,wherein different semiconductor atoms included in the second semiconductor layer are cross-linked with the NH group,wherein the second semiconductor layer comprises a concave portion between the impurity semiconductor layers, andwherein a nitrogen concentration in the second semiconductor layer gradually decreases toward the impurity semiconductor layers.
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Abstract
A thin film transistor includes, as a buffer layer, an amorphous semiconductor layer having nitrogen or an NH group between a gate insulating layer and source and drain regions and at least on the source and drain regions side. As compared to a thin film transistor in which an amorphous semiconductor is included in a channel formation region, on-current of a thin film transistor can be increased. In addition, as compared to a thin film transistor in which a microcrystalline semiconductor is included in a channel formation region, off-current of a thin film transistor can be reduced.
108 Citations
19 Claims
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1. A thin film transistor comprising:
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a gate electrode over a substrate having an insulating surface; a gate insulating layer which covers the gate electrode; a first semiconductor layer which is in contact with the gate insulating layer; a second semiconductor layer which is stacked over the first semiconductor layer; and impurity semiconductor layers forming a source region and a drain region which are in contact with part of the second semiconductor layer, wherein the second semiconductor layer comprises an amorphous semiconductor layer having an NH group or an NH2 group, wherein different semiconductor atoms included in the second semiconductor layer are cross-linked with the NH group, wherein the second semiconductor layer comprises a concave portion between the impurity semiconductor layers, and wherein a nitrogen concentration in the second semiconductor layer gradually decreases toward the impurity semiconductor layers. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A thin film transistor comprising:
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a gate electrode over a substrate having an insulating surface; a gate insulating layer which is in contact with the gate electrode; a semiconductor layer which is in contact with the gate insulating layer; impurity semiconductor layers forming a source region and a drain region; and a buffer layer which is formed between the semiconductor layer and the impurity semiconductor layers, wherein the buffer layer comprises an amorphous semiconductor layer having an NH group or an NH2 group, wherein different semiconductor atoms included in the buffer layer are cross-linked with the NH group, wherein the buffer layer comprises a concave portion between the impurity semiconductor layers, and wherein a nitrogen concentration in the buffer layer gradually decreases toward the impurity semiconductor layers. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. A semiconductor device comprising:
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a thin film transistor comprising; a gate electrode over a substrate having an insulating surface; a gate insulating layer which covers the gate electrode; a first semiconductor layer which is in contact with the gate insulating layer; a second semiconductor layer which is stacked over the first semiconductor layer; and impurity semiconductor layers forming a source region and a drain region which are in contact with part of the second semiconductor layer, wherein the second semiconductor layer comprises an amorphous semiconductor layer having an NH group or an NH2 group, wherein different semiconductor atoms included in the second semiconductor layer are cross-linked with the NH group, wherein the second semiconductor layer comprises a concave portion between the impurity semiconductor layers, and wherein a nitrogen concentration in the second semiconductor layer gradually decreases toward the impurity semiconductor layers. - View Dependent Claims (17, 18, 19)
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Specification
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Current AssigneeSemiconductor Energy Laboratory Co., Ltd.
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Original AssigneeSemiconductor Energy Laboratory Co., Ltd.
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InventorsIsa, Toshiyuki, Jinbo, Yasuhiro, Dairiki, Koji, Miyairi, Hidekazu, Yamazaki, Shunpei, Tezuka, Sachiaki
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Primary Examiner(s)Rizkallah, Kimberly
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Assistant Examiner(s)FERNANDES, ERROL V
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Application NumberUS12/490,458Publication NumberTime in Patent Office1,518 DaysField of Search257/40, 257/57, 257/263, 257/288, 257/347, 438/141, 438/149, 438/155, 438/158, 438/486US Class Current257/57CPC Class CodesH01L 27/1214 comprising a plurality of T...H01L 27/1288 employing particular maskin...H01L 29/04 characterised by their crys...H01L 29/66765 Lateral single gate single ...H01L 29/78696 characterised by the struct...
