Display device and electronic device including thin film transistor including top-gate
Objects are to provide a display device the power consumption of which is reduced, to provide a self-luminous display device the power consumption of which is reduced and which is capable of long-term use in a dark place. A circuit is formed using a thin film transistor in which a highly-purified oxide semiconductor is used and a pixel can keep a certain state (a state in which a video signal has been written). As a result, even in the case of displaying a still image, stable operation is easily performed. In addition, an operation interval of a driver circuit can be extended, which results in a reduction in power consumption of a display device. Moreover, a light-storing material is used in a pixel portion of a self-luminous display device to store light, whereby the display device can be used in a dark place for a long time.
1. A semiconductor device comprising:
a first conductive layer comprising an opening;
an oxide semiconductor layer over the first conductive layer;
a second conductive layer over the oxide semiconductor layer;
a third conductive layer over the oxide semiconductor layer;
a first insulating layer over the oxide semiconductor layer; and
a fourth conductive layer over the first insulating layer,
wherein the second conductive layer and the third conductive layer comprise the same metal material,
wherein the fourth conductive layer is configured to serve as a gate electrode,
wherein the first conductive layer is electrically connected to the oxide semiconductor layer,
wherein the second conductive layer is electrically connected to the oxide semiconductor layer,
wherein the third conductive layer is electrically connected to the oxide semiconductor layer,
wherein the third conductive layer is electrically connected to the first conductive layer, and
wherein the second conductive layer is in contact with the oxide semiconductor layer in a region overlapping with the opening of the first conductive layer.
2. The semiconductor device according to claim 1 , wherein each of the first conductive layer, the second conductive layer, the third conductive layer, and the fourth conductive layer comprises molybdenum and titanium.
3. The semiconductor device according to claim 1 ,
wherein the first conductive layer is a single-layer structure comprising molybdenum and titanium, and
wherein each of the second conductive layer, the third conductive layer, and the fourth conductive layer is a stacked-layer structure comprising copper, molybdenum, and titanium.
4. The semiconductor device according to claim 1 , wherein the third conductive layer overlaps with an edge of the oxide semiconductor layer.
5. The semiconductor device according to claim 1 , wherein the fourth conductive layer overlaps with an edge of the oxide semiconductor layer.
6. An electronic device comprising the semiconductor device according to claim 1 , wherein the electronic device is any of a portable game machine, a digital camera, a television receiver, a computer, a mobile phone, and an e-book reader.
7. A semiconductor device comprising:
a first conductive layer comprising an opening;
an oxide semiconductor layer over the first conductive layer;
a second conductive layer over the oxide semiconductor layer;
a third conductive layer over the oxide semiconductor layer;
a first insulating layer over the oxide semiconductor layer; and
a fourth conductive layer over the first insulating layer,
wherein the oxide semiconductor layer comprises indium, gallium, and zinc,
wherein the second conductive layer and the third conductive layer comprise the same metal material,
wherein the fourth conductive layer is configured to serve as a gate electrode,
wherein the first conductive layer is electrically connected to the oxide semiconductor layer,
wherein the second conductive layer is electrically connected to the oxide semiconductor layer,
wherein the third conductive layer is electrically connected to the oxide semiconductor layer,
wherein the third conductive layer is electrically connected to the first conductive layer, and
wherein the second conductive layer is in contact with the oxide semiconductor layer in a region overlapping with the opening of the first conductive layer.
8. The semiconductor device according to claim 7 , wherein each of the first conductive layer, the second conductive layer, the third conductive layer, and the fourth conductive layer comprises molybdenum and titanium.
9. The semiconductor device according to claim 7 ,
wherein the first conductive layer is a single-layer structure comprising molybdenum and titanium, and
wherein each of the second conductive layer, the third conductive layer, and the fourth conductive layer is a stacked-layer structure comprising copper, molybdenum, and titanium.
10. The semiconductor device according to claim 7 , wherein the third conductive layer overlaps with an edge of the oxide semiconductor layer.
11. The semiconductor device according to claim 7 , wherein the fourth conductive layer overlaps with an edge of the oxide semiconductor layer.
12. An electronic device comprising the semiconductor device according to claim 7 , wherein the electronic device is any of a portable game machine, a digital camera, a television receiver, a computer, a mobile phone, and an e-book reader.