Method of manufacturing a group III nitride semiconductor device and epitaxial substrate

摘要

Affords Group III nitride semiconductor devices in which the leakage current from the Schottky electrode can be decreased. In a high electron mobility transistor 1, a supporting substrate 3 is composed of AlN, AlGaN, or GaN. An Al y Ga 1- y N epitaxial layer 5 has a surface roughness (RMS) of 0.25 mm or less, wherein the surface roughness is defined by a square area measuring 1 µm per side. A GaN epitaxial layer 7 is provided between the Al y Ga 1- y N supporting substrate 3 and the Al y Ga 1- y N epitaxial layer 5. A Schottky electrode 9 is provided on the Al y Ga 1- y N epitaxial layer 5. A first ohmic electrode 11 is provided on the Al y Ga1-YN epitaxial layer 5. A second ohmic electrode 13 is provided on the Al y Ga 1- y N epitaxial layer 5. One of the first and second ohmic electrodes 11 and 13 constitutes a source electrode, and the other constitutes a drain electrode. The Schottky electrode 9 constitutes a gate electrode of the high electron mobility transistor 1.