Semiconductor device and manufacturing method thereof
View Patent ↗An object is to achieve high electrical characteristics (a high on-state current value, an excellent S value, and the like) and a highly reliable semiconductor device. A high on-state current value is achieved, whereby a further reduction in channel width (W) is achieved. A second conductive layer functioning as a gate electrode has a function of electrically surrounding side surfaces of a semiconductor film in a cross section in a channel width direction. With this structure, on-state current of a transistor can be increased. To achieve a semiconductor device with less hot-carrier degradation, the gate electrode has a tapered portion.
1. A semiconductor device comprising:
a first insulating layer over a first conductive layer;
a semiconductor layer including a channel formation region over the first insulating layer;
a second insulating layer over the semiconductor layer;
a second conductive layer over the second insulating layer; and
at least one of a source electrode and a drain electrode electrically connected to the semiconductor layer via a first opening opened in the second insulating layer,
wherein the second conductive layer covers side surfaces of the semiconductor layer with the second insulating layer positioned between the second conductive layer and the semiconductor layer,
wherein in a cross section in a channel width direction, the semiconductor layer is surrounded by the first conductive layer and the second conductive layer,
wherein the second conductive layer is electrically connected to the first conductive layer via a second opening opened in the first insulating layer and the second insulating layer, and
wherein the second opening is smaller than the first opening.
2. The semiconductor device according to claim 1 , wherein the first conductive layer and the second conductive layer have a same potential.
3. The semiconductor device according to claim 1 , wherein the semiconductor layer is a crystalline semiconductor film.
4. The semiconductor device according to claim 1 , wherein the semiconductor layer is a polysilicon film.
5. The semiconductor device according to claim 1 , wherein the first conductive layer and the second conductive layer have a light-blocking property.
6. The semiconductor device according to claim 1 , wherein the semiconductor layer includes a first impurity region in contact with the channel formation region and a second impurity region in contact with the first impurity region, and wherein the second impurity region has a higher concentration than the first impurity region.
7. The semiconductor device according to claim 1 ,
wherein the semiconductor layer includes a first impurity region in contact with the channel formation region and a second impurity region in contact with the first impurity region, and
wherein the first impurity region overlaps with the second conductive layer.
8. The semiconductor device according to claim 1 , wherein the second conductive layer has a tapered portion.
9. A semiconductor device comprising:
a first insulating layer over a first conductive layer;
a semiconductor layer including a channel formation region over the first insulating layer;
a second insulating layer over the semiconductor layer;
a second conductive layer over the second insulating layer; and
at least one of a source electrode and a drain electrode electrically connected to the semiconductor layer via a first opening opened in the second insulating layer,
wherein the second conductive layer covers side surfaces of the semiconductor layer and side surfaces of the first conductive layer,
wherein in a region where the semiconductor layer and the first conductive layer overlap with each other, a distance between the semiconductor layer and the first conductive layer is larger than or equal to a thickness of the first conductive layer,
wherein the second conductive layer is electrically connected to the first conductive layer via a second opening opened in the first insulating layer and the second insulating layer, and
wherein the second opening is smaller than the first opening.
10. The semiconductor device according to claim 9 , wherein in a cross section in a channel width direction of the semiconductor layer, an end portion of the first conductive layer projects as compared with an end surface of the semiconductor layer.
11. The semiconductor device according to claim 9 , wherein the first conductive layer and the second conductive layer have different potentials.