Semiconductor device
AssigneeSemiconductor Energy Laboratory Co., Ltd.
InventorsShunpei Yamazaki, Masayuki Sakakura, Hideomi Suzawa
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Abstract
A semiconductor device having a structure which can prevent a decrease in electrical characteristics due to miniaturization is provided. The semiconductor device includes, over an insulating surface, a stack in which a first oxide semiconductor layer and a second oxide semiconductor layer are sequentially formed, and a third oxide semiconductor layer covering part of a surface of the stack. The third oxide semiconductor layer includes a first layer in contact with the stack and a second layer over the first layer. The first layer includes a microcrystalline layer, and the second layer includes a crystalline layer in which c-axes are aligned in a direction perpendicular to a surface of the first layer.
Claims22
A semiconductor device comprising:
- a first oxide semiconductor layer over an insulating layer;
- a second oxide semiconductor layer over the first oxide semiconductor layer;
- and
- a third oxide semiconductor layer over and in contact with the insulating layer, the first oxide semiconductor layer, and the second oxide semiconductor layer,
- wherein the third oxide semiconductor layer comprises a first layer and a second layer over the first layer, and
- wherein crystallinity in the first layer is lower than crystallinity in the second layer.
A semiconductor device comprising:
- a first oxide semiconductor layer over an insulating layer;
- a second oxide semiconductor layer over the first oxide semiconductor layer;
- a third oxide semiconductor layer over and in contact with the insulating layer, the first oxide semiconductor layer, and the second oxide semiconductor layer;
- a source electrode and a drain electrode electrically connected to the first oxide semiconductor layer, the second oxide semiconductor layer, and the third oxide semiconductor layer;
- a gate insulating layer over the third oxide semiconductor layer;
- and
- a gate electrode layer over the gate insulating layer,
- wherein the third oxide semiconductor layer comprises a first layer and a second layer over the first layer, and
- wherein crystallinity in the first layer is lower than crystallinity in the second layer.
A semiconductor device comprising:
- a first oxide semiconductor layer over an insulating layer;
- a second oxide semiconductor layer over the first oxide semiconductor layer;
- and
- a third oxide semiconductor layer comprising a first region, the first region being over and in contact with the insulating layer, the first oxide semiconductor layer, and the second oxide semiconductor layer,
- wherein crystallinity in the first region is lower than crystallinity in the second oxide semiconductor layer.
Dependencies are inferred from the claim text.