Method of manufacturing nitride semiconductor device using laminated cap layers

A method of manufacturing a nitride semiconductor device, comprising:

• forming, on a substrate, a first laminated body where a first nitride semiconductor layer, a second nitride semiconductor layer, and a third nitride semiconductor layer are laminated in this order;
• subsequent to the forming, removing a partial region of the third nitride semiconductor layer;
• subsequent to the removing, implanting ions to the first nitride semiconductor layer from the partial region where the third nitride semiconductor layer is removed at least through the second nitride semiconductor layer;
• subsequent to the implanting the ions, annealing the first laminated body;
• and
• subsequent to the annealing, removing all of the second nitride semiconductor layer and the third nitride semiconductor layer which are in an active region.