<p>A nitride semiconductor device comprising: a first nitride semiconductor layer (13); a second nitride semiconductor layer (14) formed on the first nitride semiconductor layer (13) and having a larger band gap than the first nitride semiconductor layer (13); a source electrode (21), drain electrode (22) and gate electrode (23) formed on the second nitride semiconductor layer (14); a high-resistance layer (11) formed below the first nitride semiconductor layer (13); a conductive layer (32) formed in contact with the lower side of the high-resistance layer (11); a lower insulating layer (35) formed below the conductive layer (32); and a bias terminal (31) electrically connected to the conductive layer (32).</p>
