Method for manufacturing nitride semiconductor device and nitride semiconductor device

A method for manufacturing a nitride semiconductor device comprising:

• a step of forming an N-type region in a nitride semiconductor layer;
• a step of implanting ions of an acceptor element into a region located under the N-type region in the nitride semiconductor layer;
• and
• a step of forming a first P-type region located under the N-type region by subjecting the nitride semiconductor layer in which the N-type region is formed and into which ions of the acceptor element are implanted to heat treatment and activating the acceptor element,
• wherein, in the step of forming the N-type region,
• the method implants ions of a donor element into the nitride semiconductor layer at a high concentration in such a way that concentration of the donor element in the N-type region has a value equal to or greater than concentration of the acceptor element in the first P-type region, and
• in the step of implanting ions of the acceptor element into a region located under the N-type region,
• the method implants ions of the acceptor element in such a way that concentration of the acceptor element in the first P-type region is 1×1019 cm−3 or more and 1×1021 cm−3 or less.