Semiconductor device and production method

A semiconductor device comprising:

• a Group III nitride semiconductor layer including a first n-type layer, a p-type layer formed on the first n-type layer, and a second n-type layer formed on the p-type layer;
• a trench having a depth reaching from the surface of the second n-type layer to the first n-type layer, and sectionalizing the semiconductor layer into unit cells to have a predetermined planar pattern;
• and
• a recess having a depth reaching from the surface of the second n-type layer to the p-type layer,
• wherein a planar pattern of the recess is a regular polygon contained in the planar pattern of the semiconductor layer, sides of the regular polygon are not parallel to sides of the planar pattern of the semiconductor layer, a>b when a shortest distance from a corner of the trench to the recess is defined as a and a shortest distance from a side of the trench to the recess is defined as b in a plan view, and
• the Mg activation ratio is lower in the vicinity of corners of the trench than that in other regions in the vicinity of side walls of the trench of the p-type layer.