Compound semiconductor device and method of manufacturing same
A compound semiconductor device includes a substrate; a compound semiconductor layer formed on the substrate; a first insulating film formed on the compound semiconductor layer; a second insulating film formed on the first insulating film; and a gate electrode, a source electrode, and a drain electrode, each being formed on the compound semiconductor layer, wherein the gate electrode is formed of a first opening filled with a first conductive material via at least a gate insulator, and the first opening is formed in the first insulating film and configured to partially expose the compound semiconductor layer, and wherein the source electrode and the drain electrode are formed of a pair of second openings filled with at least a second conductive material, and the second openings are formed in at least the second insulating film and the first insulating film and configured to partially expose the compound semiconductor layer.
1. A method of manufacturing a compound semiconductor device, comprising:
forming a compound semiconductor layer on a substrate;
forming a first insulating film on the compound semiconductor layer;
forming a pair of first openings in the first insulating film, the pair of first openings being configured to partially expose the compound semiconductor layer;
forming a first conductive material on the first insulating film in such a manner that the first conductive material is in the first openings;
forming first masks on portions of the first conductive material corresponding to the first openings;
processing the first conductive material with the first masks to form a source electrode and a drain electrode;
forming a second insulating film on the first insulating film;
forming a second opening in at least the second insulating film;
forming a second conductive material on the second insulating film in such a manner that the second conductive material is in the second opening;
forming a second mask on a portion of the second conductive material corresponding to the second opening; and
processing the second conductive material with the second mask to form a gate electrode.
2. The method according to claim 1 , wherein the second insulating film is formed on the first insulating film in such a manner so as to cover the source electrode and the drain electrode.
3. The method according to claim 1 , wherein the compound semiconductor device is a transistor.
4. The method according to claim 1 , wherein the compound semiconductor layer comprises GaN, AlGaN, AN, InAlN, or InAlGaN.
5. The method according to claim 1 , wherein the processing of the first conductive material with the first masks comprises etching the first conductive materials in regions not covered by the first masks in order to form the source electrode and the drain electrode.
6. The method according to claim 1 , wherein the processing of the second conductive material with the second mask comprises etching the second conductive material in regions not covered by the second mask in order to form the gate electrode.
7. The method according to claim 1 , wherein the first openings are formed by isotropically etching the first insulating film, and
the second opening is formed by anisotropically etching the second insulating film so as not to expose the compound semiconductor layer and then isotropically etching the first insulating film.
8. The method according to claim 7 , wherein after a third mask is formed on the second insulating film, the anisotropic etching is performed with the third mask, and
wherein after a fourth mask is formed so as to cover the second insulating film and side faces that are processed by the anisotropic etching, the isotropic etching is performed with the fourth mask.
9. The method according to claim 7 , further comprising:
after the formation of the compound semiconductor layer and before the formation of the first insulating film, etching surface portions of the compound semiconductor layer corresponding to portions where the gate electrode, the source electrode, and the drain electrode will be formed;
after etching the surface portions, subjecting the substrate to heat treatment; and
after the heat treatment, forming an element isolation structure in an element isolation region of the compound semiconductor layer.
10. The method according to claim 1 , wherein the forming of the second opening in at least the second insulating film comprises forming the second opening to partially expose the compound semiconductor layer.
11. The method according to claim 10 , further comprising forming a gate insulator prior to forming the second conductive material.
12. The method according to claim 11 , wherein the gate insulator is formed on the second insulating film and in the second opening.
13. The method according to claim 11 , wherein the gate insulator covers an inner surface of the second opening.
14. The method according to claim 11 , wherein the gate insulator comprises AlO.