Group III nitride semiconductor device, and method for fabricating group III nitride semiconductor device

A method for fabricating a group III nitride semiconductor device, comprising the steps of:

• growing a low hydrogen content film on a semiconductor region including a group III nitride semiconductor layer, the group III nitride semiconductor layer including a p-type dopant, the low hydrogen content film being made of a material different from a group III nitride, the low hydrogen content film having a hydrogen concentration of 1×1020 cm−3 or lower, an angle between a normal axis of a primary surface of a semi-polar plane substrate and a c-axis of the semi-polar plane substrate is not lower than 45 degrees and not higher than 80 degrees or not lower than 100 degrees and not higher than 135 degrees in a waveguide axis direction of the group III nitride semiconductor device;
• and
• carrying out activation annealing of the semiconductor region to form a p-type group III nitride semiconductor layer from the group III nitride semiconductor layer, after growing the low hydrogen content film.