An AlxGayIn1-x-yN crystal substrate of the present invention has a main plane having an area of at least 10 cm2. The main plane has an outer region located within 5 mm from an outer periphery of the main plane, and an inner region corresponding to a region other than the outer region. The inner region has a total dislocation density of at least 1×102 cm−2 and at most 1×106 cm−2. It is thereby possible to provide an AlxGayIn1-x-yN crystal substrate having a large size and a suitable dislocation density for serving as a substrate for a semiconductor device, a semiconductor device including the AlxGayIn1-x-yN crystal substrate, and a method of manufacturing the same.