A method of manufacturing a thin-film transistor (TFT) and a TFT are provided. The method of manufacturing the TFT includes, after depositing a semiconductor layer, oxidizing regions of the semiconductor layer corresponding to sputtering target gaps, so that oxygen vacancies at the regions corresponding to the sputtering target gaps can be decreased and oxygen vacancies on the semiconductor layer can be more uniform.

A method of manufacturing a thin-film transistor (TFT) and a TFT are provided. The method of manufacturing the TFT includes, after depositing a semiconductor layer, oxidizing regions of the semiconductor layer corresponding to sputtering target gaps, so that oxygen vacancies at the regions corresponding to the sputtering target gaps can be decreased and oxygen vacancies on the semiconductor layer can be more uniform.

A semiconductor device having favorable electrical characteristics is provided. The semiconductor device is manufactured by a first step of forming a semiconductor layer containing a metal oxide, a second step of forming a first insulating layer, a third step of forming a first conductive film over the first insulating layer, a fourth step of etching part of the first conductive film to form a first conductive layer, thereby forming a first region over the semiconductor layer that overlaps with the first conductive layer and a second region over the semiconductor layer that does not overlap with the first conductive layer, and a fifth step of performing first treatment on the conductive layer. The first treatment is plasma treatment in an atmosphere including a mixed gas of a first gas containing an oxygen element but not containing a hydrogen element, and a second gas containing a hydrogen element but not containing an oxygen element.

A semiconductor device having favorable electrical characteristics is provided. The semiconductor device is manufactured by a first step of forming a semiconductor layer containing a metal oxide, a second step of forming a first insulating layer, a third step of forming a first conductive film over the first insulating layer, a fourth step of etching part of the first conductive film to form a first conductive layer, thereby forming a first region over the semiconductor layer that overlaps with the first conductive layer and a second region over the semiconductor layer that does not overlap with the first conductive layer, and a fifth step of performing first treatment on the conductive layer. The first treatment is plasma treatment in an atmosphere including a mixed gas of a first gas containing an oxygen element but not containing a hydrogen element, and a second gas containing a hydrogen element but not containing an oxygen element.

A semiconductor device includes: a semiconductor substrate; a semiconductor layer of a first conductivity type that is deposited on a surface of the semiconductor substrate; a trench that is formed on a surface of the semiconductor layer; an insulating film that covers a bottom surface of the trench and a lateral surface of the trench; a conductive body that fills inside the trench that is covered by the insulating film; a second conductive type region that is formed in the semiconductor layer, is arranged under the trench, and is within a region of the trench in a plan view of the semiconductor substrate; and a metal film that is electrically connected to the conductive body and forms a Schottky barrier with the surface of the semiconductor layer.

In a transistor that includes an oxide semiconductor, a change in electrical characteristics is suppressed and the reliability is improved. A semiconductor device that includes a transistor is provided. The transistor includes a first conductive film that functions as a first gate electrode, a first gate insulating film, a first oxide semiconductor film that includes a channel region, a second gate insulating film, and a second oxide semiconductor film and a second conductive film that function as a second gate electrode. The second oxide semiconductor film includes a region higher in carrier density than the first oxide semiconductor film. The second conductive film includes a region in contact with the first conductive film.

A semiconductor device includes thin film transistors each having an oxide semiconductor. The oxide semiconductor has a channel region, a drain region, a source region, and low concentration regions which are lower in impurity concentration than the drain region and the source region. The low concentration regions are located between the channel region and the drain region, and between the channel region and the source region. Each of the thin film transistors has a gate insulating film on the channel region and the low concentration regions, an aluminum oxide film on a first part of the gate insulating film, the first part being located on the channel region, and a gate electrode on the aluminum oxide film and a second part of the gate insulating film, the second part being located on the low concentration regions.

A semiconductor device includes thin film transistors each having an oxide semiconductor. The oxide semiconductor has a channel region, a drain region, a source region, and low concentration regions which are lower in impurity concentration than the drain region and the source region. The low concentration regions are located between the channel region and the drain region, and between the channel region and the source region. Each of the thin film transistors has a gate insulating film on the channel region and the low concentration regions, an aluminum oxide film on a first part of the gate insulating film, the first part being located on the channel region, and a gate electrode on the aluminum oxide film and a second part of the gate insulating film, the second part being located on the low concentration regions.

A semiconductor device includes thin film transistors each having an oxide semiconductor. The oxide semiconductor has a channel region, a drain region, a source region, and low concentration regions which are lower in impurity concentration than the drain region and the source region. The low concentration regions are located between the channel region and the drain region, and between the channel region and the source region. Each of the thin film transistors has a gate insulating film on the channel region and the low concentration regions, an aluminum oxide film on a first part of the gate insulating film, the first part being located on the channel region, and a gate electrode on the aluminum oxide film and a second part of the gate insulating film, the second part being located on the low concentration regions.

A semiconductor device includes thin film transistors each having an oxide semiconductor. The oxide semiconductor has a channel region, a drain region, a source region, and low concentration regions which are lower in impurity concentration than the drain region and the source region. The low concentration regions are located between the channel region and the drain region, and between the channel region and the source region. Each of the thin film transistors has a gate insulating film on the channel region and the low concentration regions, an aluminum oxide film on a first part of the gate insulating film, the first part being located on the channel region, and a gate electrode on the aluminum oxide film and a second part of the gate insulating film, the second part being located on the low concentration regions.