A composite substrate of the present disclosure is composed of two parts: a SiC substrate; and a Si-containing thermal-sprayed layer made of a material obtained by melting Si or a Si alloy through thermal spraying. The Si-containing thermal-sprayed layer serves as a support substrate for supporting the SiC substrate so as to keep the mechanical strength thereof, and is provided at one surface of the SiC substrate on the side opposite to a surface where a nitride semiconductor layer composed of layers made of nitride semiconductors such as an AlN buffer layer, a GaN buffer layer, and an AlGaN Schottky layer is formed through epitaxial growth.

A semiconductor device includes a layered body, a gate electrode, a source electrode, a drain electrode, and a cap layer. The layered body includes a channel layer and a first low resistance region. The channel layer is made of a compound semiconductor. The first low resistance region is provided in a portion on surface side of the layered body. The gate electrode, the source electrode, and the drain electrode are each provided on top surface side of the layered body. The cap layer is provided between the first low resistance region and one or both of the source electrode and the drain electrode.

A semiconductor device includes a layered body, a gate electrode, a source electrode, a drain electrode, and a cap layer. The layered body includes a channel layer and a first low resistance region. The channel layer is made of a compound semiconductor. The first low resistance region is provided in a portion on surface side of the layered body. The gate electrode, the source electrode, and the drain electrode are each provided on top surface side of the layered body. The cap layer is provided between the first low resistance region and one or both of the source electrode and the drain electrode.

A new and useful p-type oxide semiconductor with a wide band gap and an enhanced electrical conductivity and the method of manufacturing the p-type oxide semiconductor are provided. A method of manufacturing a p-type oxide semiconductor including: generating atomized droplets by atomizing a raw material solution containing at least a d-block metal in the periodic table and a metal of Group 13 of the periodic table; carrying the atomized droplets onto a surface of a base by using a carrier gas; causing a thermal reaction of the atomized droplets adjacent to the surface of the base under an atmosphere of oxygen to form the p-type oxide semiconductor on the base.

A new and useful p-type oxide semiconductor with a wide band gap and an enhanced electrical conductivity and the method of manufacturing the p-type oxide semiconductor are provided. A method of manufacturing a p-type oxide semiconductor including: generating atomized droplets by atomizing a raw material solution containing at least a d-block metal in the periodic table and a metal of Group 13 of the periodic table; carrying the atomized droplets onto a surface of a base by using a carrier gas; causing a thermal reaction of the atomized droplets adjacent to the surface of the base under an atmosphere of oxygen to form the p-type oxide semiconductor on the base.

A semiconductor device includes a semiconductor substrate configured to include a channel, a gate supported by the semiconductor substrate to control current flow through the channel, a first dielectric layer supported by the semiconductor substrate and including an opening in which the gate is disposed, and a second dielectric layer disposed between the first dielectric layer and a surface of the semiconductor substrate in a first area over the channel. The gate may be configured to include a lateral overhang that is separated from an upper surface of the first dielectric layer.

A semiconductor device includes a semiconductor substrate configured to include a channel, first and second ohmic contacts supported by the semiconductor substrate, in ohmic contact with the semiconductor substrate, and spaced from one another for current flow between the first and second ohmic contacts through the channel, and first and second dielectric layers supported by the semiconductor substrate. At least one of the first and second ohmic contacts extends through respective openings in the first and second dielectric layers. The second dielectric layer is disposed between the first dielectric layer and a surface of the semiconductor substrate, and the second dielectric layer includes a wet etchable material having an etch selectivity to a dry etchant of the first dielectric layer.

The present invention discloses a method for preparing a GaN rectifier suitable for operating at an alternating current frequency of 35 GHz: sequentially growing, on a silicon substrate, an N-polar GaN buffer layer, a carbon doped semi-insulated N-polar GaN layer, a non-doped N-polar AlGaN layer, a non-doped N-polar GaN layer and a non-doped N-polar InGaN thin film to obtain a rectifier epitaxial wafer; preparing a pattern groove for a schottky contact electrode on the GaN rectifier epitaxial wafer, and depositing the schottky contact electrode in the groove; preparing a pattern for an ohmic contact electrode, and depositing a device ohmic contact electrode on the surface of the epitaxial wafer; subsequently, depositing a silicon nitride passivation layer at a part where there is no electrode on the surface of the epitaxial wafer, and preparing a surface electrode area; and finally, performing mesa isolation treatment on the GaN rectifier epitaxial wafer. The present invention realizes the preparation of a high-frequency GaN rectifier, and improves the performance stability of a rectifier device operating at a high power.

The present invention discloses a method for preparing a GaN rectifier suitable for operating at an alternating current frequency of 35 GHz: sequentially growing, on a silicon substrate, an N-polar GaN buffer layer, a carbon doped semi-insulated N-polar GaN layer, a non-doped N-polar AlGaN layer, a non-doped N-polar GaN layer and a non-doped N-polar InGaN thin film to obtain a rectifier epitaxial wafer; preparing a pattern groove for a schottky contact electrode on the GaN rectifier epitaxial wafer, and depositing the schottky contact electrode in the groove; preparing a pattern for an ohmic contact electrode, and depositing a device ohmic contact electrode on the surface of the epitaxial wafer; subsequently, depositing a silicon nitride passivation layer at a part where there is no electrode on the surface of the epitaxial wafer, and preparing a surface electrode area; and finally, performing mesa isolation treatment on the GaN rectifier epitaxial wafer. The present invention realizes the preparation of a high-frequency GaN rectifier, and improves the performance stability of a rectifier device operating at a high power.

A semiconductor element includes a high-resistivity substrate that includes a β-Ga.sub.2O.sub.3-based single crystal including an acceptor impurity, an undoped β-Ga.sub.2O.sub.3-based single crystal layer formed on the high-resistivity substrate, and an n-type channel layer that includes a side surface surrounded by the undoped β-Ga.sub.2O.sub.3-based single crystal layer. The undoped β-Ga.sub.2O.sub.3-based single crystal layer includes an element isolation region.