The purpose of the invention is suppressing a kink phenomenon and improvoning the image quality of a display device. The display device has a TFT in a pixel. The TFT has a semiconductor layer, a first insulating layer under the semiconductor layer, a second insulating layer over the semiconductor layer, and a gate electrode facing the semiconductor layer with a gap. The gate electrode has a first gate electrode portion facing a lower surface of the semiconductor layer, a second gate electrode portion facing an upper surface of the semiconductor layer, and a third gate electrode portion facing a lateral surface of the semiconductor layer and connected to the first and second gate electrode portions. A laminated part where the first and second insulating layers are stacked is around the semiconductor layer, and a part of the laminated part is between the lateral surface and the third gate electrode portion.

A display device in which parasitic capacitance between wirings can be reduced is provided. Furthermore, a display device in which display quality is improved is provided. Furthermore, a display device in which power consumption can be reduced is provided. The display device includes a signal line, a scan line, a first electrode, a second electrode, a third electrode, a first pixel electrode, a second pixel electrode, and a semiconductor film. The signal line intersects with the scan line, the first electrode is electrically connected to the signal line, the first electrode has a region overlapping with the scan line, the second electrode faces the first electrode, the third electrode faces the first electrode, the first pixel electrode is electrically connected to the second electrode, the second pixel electrode is electrically connected to the third electrode, the semiconductor film is in contact with the first electrode, the second electrode, and the third electrode, and the semiconductor film is provided between the scan line and the first electrode to the third electrode.

A minute transistor is provided. A transistor with low parasitic capacitance is provided. A transistor having high frequency characteristics is provided. A transistor having a high on-state current is provided. A semiconductor device including the transistor is provided. A semiconductor device having a high degree of integration is provided. A semiconductor device including an oxide semiconductor; a second insulator; a second conductor; a third conductor; a fourth conductor; a fifth conductor; a first conductor and a first insulator embedded in an opening portion formed in the second insulator, the second conductor, the third conductor, the fourth conductor, and the fifth conductor; a region where a side surface and a bottom surface of the second conductor are in contact with the fourth conductor; and a region where a side surface and a bottom surface of the third conductor are in contact with the fifth conductor.

A semiconductor device that is suitable for miniaturization and higher density is provided. A semiconductor device includes a first transistor over a semiconductor substrate, a second transistor including an oxide semiconductor over the first transistor, and a capacitor over the second transistor. The capacitor includes a first conductor, a second conductor, and an insulator. The second conductor covers a side surface of the first conductor with an insulator provided therebetween.

A novel metal oxide is provided. A semiconductor device with favorable electrical characteristics is provided. The metal oxide has a plurality of energy gaps, and includes a first region having a high energy level of a conduction band minimum and a second region having an energy level of a conduction band minimum lower than that of the first region. The second region includes more carriers than the first region. A difference between the energy level of the conduction band minimum of the first region and the energy level of the conduction band minimum of the second region is greater than or equal to 0.2 eV.

A novel metal oxide or a novel sputtering target is provided. A sputtering target includes a conductive material and an insulating material. The insulating material includes an oxide, a nitride, or an oxynitride including an element M1. The element M1 is one or more kinds of elements selected from Al, Ga, Si, Mg, Zr, Be, and B. The conductive material includes an oxide, a nitride, or an oxynitride including indium and zinc. A metal oxide film is deposited using the sputtering target in which the conductive material and the insulating material are separated from each other.

A novel metal oxide is provided. The metal oxide has a plurality of energy gaps, and includes a first region having a high energy level of a conduction band minimum and a second region having an energy level of a conduction band minimum lower than that of the first region. The second region comprises more carriers than the first region. A difference between the energy level of the conduction band minimum of the first region and the energy level of the conduction band minimum of the second region is 0.2 eV or more. The energy gap of the first region is greater than or equal to 3.3 eV and less than or equal to 4.0 eV and the energy gap of the second region is greater than or equal to 2.2 eV and less than or equal to 2.9 eV.

Disclosed are semiconductor devices including a double gate metal oxide semiconductor (MOS) transistor and methods for fabricating the same. The double gate MOS transistor includes a first back gate, a second back gate, and a first dielectric layer disposed on the first back gate and on the second back gate. An MX2 material layer is disposed on the first dielectric layer, a second dielectric layer disposed on the MX2 material layer, and a work function metal (WFM) is disposed on the second dielectric layer. A front gate is disposed on the WFM, which fills a space between the first back gate and the second back.

An object is to provide a display device which operates stably with use of a transistor having stable electric characteristics. In manufacture of a display device using transistors in which an oxide semiconductor layer is used for a channel formation region, a gate electrode is further provided over at least a transistor which is applied to a driver circuit. In manufacture of a transistor in which an oxide semiconductor layer is used for a channel formation region, the oxide semiconductor layer is subjected to heat treatment so as to be dehydrated or dehydrogenated; thus, impurities such as moisture existing in an interface between the oxide semiconductor layer and the gate insulating layer provided below and in contact with the oxide semiconductor layer and an interface between the oxide semiconductor layer and a protective insulating layer provided on and in contact with the oxide semiconductor layer can be reduced.

An object is to improve reliability of a light-emitting device. A light-emitting device has a driver circuit portion including a transistor for a driver circuit and a pixel portion including a transistor for a pixel over one substrate. The transistor for the driver circuit and the transistor for the pixel are inverted staggered transistors each including an oxide semiconductor layer in contact with part of an oxide insulating layer. In the pixel portion, a color filter layer and a light-emitting element are provided over the oxide insulating layer. In the transistor for the driver circuit, a conductive layer overlapping with a gate electrode layer and the oxide semiconductor layer is provided over the oxide insulating layer. The gate electrode layer, a source electrode layer, and a drain electrode layer are formed using metal conductive films.