The reliability of a transistor including an oxide semiconductor can be improved by suppressing a change in electrical characteristics. A transistor included in a semiconductor device includes a first oxide semiconductor film over a first insulating film, a gate insulating film over the first oxide semiconductor film, a second oxide semiconductor film over the gate insulating film, and a second insulating film over the first oxide semiconductor film and the second oxide semiconductor film. The first oxide semiconductor film includes a channel region in contact with the gate insulating film, a source region in contact with the second insulating film, and a drain region in contact with the second insulating film. The second oxide semiconductor film has a higher carrier density than the first oxide semiconductor film.

Provided are an oxide sintered compact whereby low carrier density and high carrier mobility are obtained when the oxide sintered compact is used to obtain an oxide semiconductor thin film by a sputtering method, and a sputtering target which uses the oxide sintered compact. This oxide sintered compact contains oxides of indium, gallium, and aluminum. The gallium content is from 0.15 to 0.49 by Ga/(In+Ga) atomic ratio, and the aluminum content is from 0.0001 to less than 0.25 by Al/(In+Ga+Al) atomic ratio. A crystalline oxide semiconductor thin film formed using this oxide sintered compact as a sputtering target is obtained at a carrier density of 4.0×10.sup.18 cm.sup.−3 or less and a carrier mobility of 10 cm.sup.−2V.sup.−1sec.sup.−1 or greater.

Provided are an oxide sintered compact whereby low carrier density and high carrier mobility are obtained when the oxide sintered compact is used to obtain an oxide semiconductor thin film by a sputtering method, and a sputtering target which uses the oxide sintered compact. This oxide sintered compact contains oxides of indium, gallium, and aluminum. The gallium content is from 0.15 to 0.49 by Ga/(In+Ga) atomic ratio, and the aluminum content is from 0.0001 to less than 0.25 by Al/(In+Ga+Al) atomic ratio. A crystalline oxide semiconductor thin film formed using this oxide sintered compact as a sputtering target is obtained at a carrier density of 4.0×10.sup.18 cm.sup.−3 or less and a carrier mobility of 10 cm.sup.−2V.sup.−1sec.sup.−1 or greater.

According to one embodiment, a semiconductor device includes contact holes passing through a source region of a drain region of an interlayer insulating film and oxide semiconductor layer to reach an insulating substrate, wherein a source electrode and a drain electrode are formed inside the contact holes, respectively.

According to one embodiment, a semiconductor device includes contact holes passing through a source region of a drain region of an interlayer insulating film and oxide semiconductor layer to reach an insulating substrate, wherein a source electrode and a drain electrode are formed inside the contact holes, respectively.

The disclosure provides a semiconductor apparatus capable of keeping a semiconductor characteristics and realizing excellent semiconductor properties even when using an n type semiconductor (gallium oxide, for example) having a low loss at a high voltage and having much higher dielectric breakdown electric field strength than SiC. A semiconductor apparatus includes a gate electrode and a channel layer formed of a channel directly or through other layers on a side wall of the gate electrode, and wherein a portion of or whole the channel layer may be a p type oxide semiconductor (iridium oxide, for example).

The disclosure provides a semiconductor apparatus capable of keeping a semiconductor characteristics and realizing excellent semiconductor properties even when using an n type semiconductor (gallium oxide, for example) having a low loss at a high voltage and having much higher dielectric breakdown electric field strength than SiC. A semiconductor apparatus includes a gate electrode and a channel layer formed of a channel directly or through other layers on a side wall of the gate electrode, and wherein a portion of or whole the channel layer may be a p type oxide semiconductor (iridium oxide, for example).

Various technologies are described herein pertaining to electrochemical etching of a semiconductor controlled by way of a laser that emits light with an energy below a bandgap energy of the semiconductor.

To provide a method by which a semiconductor device including a thin film transistor with excellent electric characteristics and high reliability is manufactured with a small number of steps. After a channel protective layer is formed over an oxide semiconductor film containing In, Ga, and Zn, a film having n-type conductivity and a conductive film are formed, and a resist mask is formed over the conductive film. The conductive film, the film having n-type conductivity, and the oxide semiconductor film containing In, Ga, and Zn are etched using the channel protective layer and gate insulating films as etching stoppers with the resist mask, so that source and drain electrode layers, a buffer layer, and a semiconductor layer are formed.

To provide a method by which a semiconductor device including a thin film transistor with excellent electric characteristics and high reliability is manufactured with a small number of steps. After a channel protective layer is formed over an oxide semiconductor film containing In, Ga, and Zn, a film having n-type conductivity and a conductive film are formed, and a resist mask is formed over the conductive film. The conductive film, the film having n-type conductivity, and the oxide semiconductor film containing In, Ga, and Zn are etched using the channel protective layer and gate insulating films as etching stoppers with the resist mask, so that source and drain electrode layers, a buffer layer, and a semiconductor layer are formed.