Ohmic electrode structure of nitride semiconductor device

An ohmic electrode structure of a nitride semiconductor device having a nitride semiconductor, comprising:

• a first metal film formed on the nitride semiconductor, and
• a second metal film formed on the first metal film,
• wherein the first metal film is made of at least one material selected from the group consisting of V, Mo, Ti, Nb, W, Fe, Hf, Re, Ta, and Zr, and
• the second metal film is made of at least one material that is different from that of the first metal film and selected from the group consisting of V, Mo, Ti, Nb, W, Fe, Hf, Re, Ta, Zr, Pt, and Au,
• excluding;
• a combination of V as the first metal film and Pt or Au as the second metal film,
• a combination of Ti as the first metal film and Mo, Pt or Au as the second metal film,
• a combination of W as the first metal film and Pt or Au as the second metal film,
• a combination of Hf as the first metal film and Au as the second metal film, and
• a combination of Zr as the first metal film and Pt or Au as the second metal film.

An ohmic electrode structure of a nitride semiconductor device having a nitride semiconductor, comprising:

• a first metal film formed on the nitride semiconductor,
• a second metal film formed on the first metal film, and
• a third metal film formed on the second metal film,
• wherein the first metal film is made of at least one material selected from the group consisting of V, Mo, Ti, Nb, W, Fe, Hf, Re, Ta, and Zr,
• the second metal film is made of at least one material that is different from that of the first metal film and selected from the group consisting of V, Mo, Ti, Nb, W, Fe, Hf, Re, Ta, Zr, Pt, and Au, and
• the third metal film is made of at least one material that is different from that of the second metal film and selected from the group consisting of V, Mo, Ti, Nb, W, Fe, Hf, Re, Ta, Zr, Pt, and Au,
• excluding;
• a combination of V as the first metal film and Pt or Au as the second metal film,
• a combination of Ti as the first metal film and Mo, Pt or Au as the second metal film,
• a combination of W as the first metal film and Pt or Au as the second metal film,
• a combination of Hf as the first metal film and Au as the second metal film,
• a combination of Zr as the first metal film and Pt or Au as the second metal film, and
• a combination of Ti as the first metal film, Pt as the second metal film, and Au as the third metal film.

A method of manufacturing an ohmic electrode structure of a nitride semiconductor device having a nitride semiconductor, comprising the steps of:

• forming a first metal film on the nitride semiconductor,
• forming a second metal film on the first metal film, and
• performing a heat treatment after forming the second metal film,
• wherein the first metal film is made of at least one material selected from the group consisting of V, Mo, Ti, Nb, W, Fe, Hf, Re, Ta, and Zr, and
• the second metal film is made of at least one material that is different from that of the first metal film and selected from the group consisting of V, Mo, Ti, Nb, W, Fe, Hf, Re, Ta, Zr, Pt, and Au,
• excluding;
• a combination of V as the first metal film and Pt or Au as the second metal film,
• a combination of Ti as the first metal film and Mo, Pt or Au as the second metal film,
• a combination of W as the first metal film and Pt or Au as the second metal film,
• a combination of Hf as the first metal film and Au as the second metal film, and
• a combination of Zr as the first metal film and Pt or Au as the second metal film.

A method of manufacturing an ohmic electrode structure of a nitride semiconductor device having a nitride semiconductor, comprising the steps of:

• forming a first metal film on the nitride semiconductor,
• forming a second metal film on the first metal film,
• forming a third metal film on the second metal film, and
• performing a heat treatment after forming the third metal film,
• wherein the first metal film is made of at least one material selected from the group consisting of V, Mo, Ti, Nb, W, Fe, Hf, Re, Ta, and Zr,
• the second metal film is made of at least one material that is different from that of the first metal film and selected from the group consisting of V, Mo, Ti, Nb, W, Fe, Hf, Re, Ta, Zr, Pt, and Au, and
• the third metal film is made of at least one material that is different from that of the second metal film and selected from the group consisting of V, Mo, Ti, Nb, W, Fe, Hf, Re, Ta, Zr, Pt, and Au,
• excluding;
• a combination of V as the first metal film and Pt or Au as the second metal film,
• a combination of Ti as the first metal film and Mo, Pt or Au as the second metal film,
• a combination of W as the first metal film and Pt or Au as the second metal film,
• a combination of Hf as the first metal film and Au as the second metal film,
• a combination of Zr as the first metal film and Pt or Au as the second metal film, and
• a combination of Ti as the first metal film, Pt as the second metal film, and Au as the third metal film.