A semiconductor device with an improved arithmetic processing speed and a decreased circuit size, and its driving method are provided. In the semiconductor device, a first terminal of a first transistor and a gate of a second transistor are electrically connected to a first terminal of a capacitor, and a control circuit is electrically connected to a second terminal of the capacitor. The control circuit supplies a first potential to the second terminal of the capacitor, in other words, adds a value corresponding to the first potential to the value of first data previously retained in the gate of the second transistor in order to obtain second data. In the second transistor, the second data, specifically, a third potential commensurate with the potential of the gate will be output from a second terminal when a second potential is supplied to a first terminal.

A semiconductor device that can operate at high speed or having high strength against stress is provided. One embodiment of the present invention is a semiconductor device including a semiconductor film including a channel formation region and a pair of impurity regions between which the channel formation region is positioned; a gate electrode overlapping side and top portions of the channel formation region with an insulating film positioned between the gate electrode and the side and top portions; and a source electrode and a drain electrode in contact with side and top portions of the pair of impurity regions.

To provide a semiconductor device with small parasitic capacitance. Alternatively, to provide a semiconductor device with low power consumption. The semiconductor device includes a transistor and a capacitor. The transistor includes a first conductor, a first insulator over the first conductor, a semiconductor including a region overlapping with the first conductor with the first insulator interposed therebetween, a second insulator over the semiconductor, a second conductor including a region overlapping with the semiconductor with the second insulator interposed therebetween, and a third conductor and a fourth conductor including a region in contact with a top surface of the semiconductor. The capacitor includes a layer formed from the same layer as the first conductor and a layer formed from the same layer as the third conductor and the fourth conductor.

Hall effect devices and field effect transistors are formed incorporating a carbon-based nanostructure layer such as carbon nanotubes and/or graphene with a sacrificial metal layer formed there over to protect the carbon-based nanostructure layer during processing.

A dual gate oxide semiconductor TFT substrate is made by utilizing a halftone mask to implement one photo process, which accomplishes patterning of an oxide semiconductor layer and forms an oxide conductor layer with ion doping process. Patterning of a bottom gate isolation layer and a top gate isolation layer are performed at the same time with one photo process. A first top gate, a first source, a first drain, a second top gate, a second source, and a second drain are formed at the same time with one photo process. Patterning of a flat layer, a passivation layer, and a top gate isolation layer are performed at the same time with one photo process. As such, the number of photo processes applied to manufacture the TFT substrate is reduced to five and the manufacturing process is shortened to thereby raise the production efficiency and lower the production cost.

A method including providing a substrate with a gate, a layer of gate insulator material adjacent the gate, and a layer of metal oxide semiconductor material positioned on the gate insulator opposite the gate, forming a selectively patterned etch stop passivation layer and heating at elevated temperature in an oxygen-containing or nitrogen-containing or inert ambience to selectively increase the carrier concentration in regions of the metal oxide semiconductor not covered by the etch stop layer, on which overlying and spaced apart source/drain metals are formed. Subsequently heating the transistor in an oxygen-containing or nitrogen-containing or inert ambience to further improve the source/drain contacts and adjust the threshold voltage to a desired level. Providing additional passivation layer(s) on top of the transistor with electric insulation and barrier property to moisture and chemicals in the surrounding environment.

A display device includes a pixel including a thin film transistor, and an under layer below the thin film transistor. The thin film transistor includes a first gate electrode, a semiconductor layer and a second gate electrode. The semiconductor layer includes a channel region that overlaps at least one of the first gate electrode and the second gate electrode in a plan view. The channel region curves in a thickness direction of the semiconductor layer. The first gate electrode includes a first edge located on the side of an edge of the channel region in a direction of a channel length. The second gate electrode includes a second edge located on the side of the edge of the channel region. The position of the first edge is different from the position of the second edge in the direction of the channel length.

A semiconductor device provided with a plurality of kinds of transistors with different device structures suitable for functions of circuits is provided. The semiconductor device includes first to third transistors with different device structures over one substrate. A semiconductor layer of the first transistor is an oxide semiconductor film with a stacked-layer structure, and a semiconductor layer of each of the second and third transistors is an oxide semiconductor film with a single-layer structure. Each of the first and second transistors includes a back gate electrode connected to its gate electrode.

A transistor having favorable electrical characteristics. A transistor suitable for miniaturization. A transistor having a high switching speed. One embodiment of the present invention is a semiconductor device that includes a transistor. The transistor includes an oxide semiconductor, a gate electrode, and a gate insulator. The oxide semiconductor includes a first region in which the oxide semiconductor and the gate electrode overlap with each other with the gate insulator positioned therebetween. The transistor has a threshold voltage higher than 0 V and a switching speed lower than 100 nanoseconds.

A thin-film transistor (TFT) switch includes a gate, a drain, a source, a semiconductor layer, and a fourth electrode. The drain is connected to a first signal. The gate is connected to a control signal to control the switch on or off. The source outputs the first signal when the switch turns on. The fourth electrode and the gate are respectively located at two sides of the semiconductor layer. The fourth electrode is conductive and is selectively coupled to different voltage levels, thereby reducing leakage current in a channel to improve switch characteristic when the switch turns off.