An n.sup.-type epitaxial layer is grown on a front surface of the silicon carbide substrate by a CVD method in a mixed gas atmosphere containing a source gas, a carrier gas, a doping gas, an additive gas, and a gas containing vanadium. The doping gas is nitrogen gas; and the gas containing vanadium is vanadium tetrachloride gas. In the mixed gas atmosphere, the vanadium bonds with the nitrogen, producing vanadium nitride, whereby the nitrogen concentration in the mixed gas atmosphere substantially decreases. As a result, the nitrogen taken in by the n.sup.-type epitaxial layer decreases and the n.sup.-type epitaxial layer including nitrogen and vanadium as dopants is grown having a low impurity concentration.

A Ga.sub.2O.sub.3-based semiconductor element includes an undoped -Ga.sub.2O.sub.3 single crystal film disposed on a surface of a -Ga.sub.2O.sub.3 substrate, a source electrode and a drain electrode disposed on a same side of the undoped -Ga.sub.2O.sub.3 single crystal film, a gate electrode disposed on the undoped -Ga.sub.2O.sub.3 single crystal film between the source electrode and the drain electrode, and a region formed in the undoped -Ga.sub.2O.sub.3 single crystal film under the source electrode and the drain electrode and including a controlled dopant concentration.

A film formation device which forms a film on a substrate through the heat treatment of a starting material solution in the form of a mist, the film formation device including a mist conversion unit that generates a mist by converting the starting material solution into mist, a carrier gas supply unit that supplies a carrier gas for transporting the mist generated by the mist conversion unit, a film formation unit that includes therein a placement part for placing the substrate and that is where the mist transported by the carrier gas is supplied onto the substrate, and an exhaust unit that exhausts exhaust gas from the film formation unit, and further including, above the placement part in the film formation unit, a nozzle for supplying the mist onto the substrate and a top plate for adjusting the flow of the mist supplied from the nozzle.

A film-forming method for heat-treating a raw material solution atomized into a mist and performing a film-formation, and the method includes the following steps: atomizing the raw material solution or making the raw material solution into droplets to generate a mist; conveying the mist to a film-forming part by a carrier gas; and supplying the mist from a nozzle to a substrate, heat-treating the mist on the substrate, and performing the film-formation in the film-forming part, wherein with the area of an opening surface of the nozzle being S [cm.sup.2], the longest distance among distances between points in the opening surface and the surface of the substrate being H [cm], and the flow rate of the carrier gas supplied from the nozzle being Q [L/min], SH/Q?0.015 results.

An object of the present invention is to provide a film formation technique having high productivity by realizing a foundation layer having excellent crystallinity with a small film thickness of about 2 m. An embodiment of the present invention relates to a film forming method which includes the step of forming a buffer layer by sputtering on a sapphire substrate held by a substrate holder. The buffer layer includes an epitaxial film having a wurtzite structure prepared by adding at least one substance selected from the group consisting of C, Si, Ge, Mg, Zn, Mn, and Cr to Al.sub.xGa.sub.1xN (where 0x1).

In a first aspect of a present inventive subject matter, a semiconductor device includes an n-type semiconductor layer including a first semiconductor as a major component, an i-type semiconductor layer including a second semiconductor as a major component and a p-type semiconductor layer including a third semiconductor as a major component. The second semiconductor contains a corundum-structured oxide semiconductor.

In a first aspect of a present inventive subject matter, a semiconductor device includes an n-type semiconductor layer, an i-type semiconductor layer and a p-type semiconductor layer. The i-type semiconductor layer includes an oxide semiconductor as a major component. The oxide semiconductor that is included as the major component of the i-type semiconductor layer includes at least one metal selected from among aluminum, indium, and gallium.

A coating liquid for forming an n-type oxide semiconductor film, the coating liquid including: a Group A element, which is at least one selected from the group consisting of Sc, Y, Ln, B, Al, and Ga; a Group B element, which is at least one of In and Tl; a Group C element, which is at least one selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, Group 7 elements, Group 8 elements, Group 9 elements, Group 10 elements, Group 14 elements, Group 15 elements, and Group 16 elements; and a solvent.

A large Group III nitride crystal of high quality with few defects such as a distortion, a dislocation, and warping is produced by vapor phase epitaxy. A method for producing a Group III nitride crystal includes: a first Group III nitride crystal production process of producing a first Group III nitride crystal 1003 by liquid phase epitaxy; and a second Group III nitride crystal production process of producing a second Group III nitride crystal 1004 on the first crystal 1003 by vapor phase epitaxy by causing a Group III element metal to react with an oxidizing agent and nitrogen-containing gas. In the first Group III nitride crystal production process, the surfaces of seed crystals 1003a (preliminarily provided Group III nitride) are brought into contact with an alkali metal melt, a Group III element and nitrogen are cause to react with each other in a nitrogen-containing atmosphere in the alkali metal melt, and the Group III nitride crystals are bound together by growth of the Group III nitride crystals grown from the seed crystals 1003a to produce a first crystal 1003.

A semiconductor device is provided that is excellent in semiconductor properties and Schottky characteristics. A semiconductor device includes: a semiconductor layer containing a crystalline oxide semiconductor with a corundum structure as a major component; and a Schottky electrode on the semiconductor layer, wherein the Schottky electrode is formed by containing a metal of Groups 4-9 of the periodic table, thereby manufacturing a semiconductor device excellent in semiconductor properties and Schottky characteristics without impairing the semiconductor properties to use the semiconductor device thus obtained for a power device and the like.