Method of Manufacturing III Nitride Crystal, III Nitride Crystal Substrate, and Semiconductor Device

A III-nitride crystal substrate comprising:

• an undersubstrate constituted by a plurality of first III-nitride crystal plates each defining a major face and adjoining one another so as to form a major-face collective surface, said plates being:
• conditioned to a deviation in crystallographic plane orientation in any given point on the major face of each crystal plate, with respect to an {hkil} plane being a crystallographic plane chosen exclusive of the {0001} form, of not greater than 0.5°, and
• arranged in a manner such that the plane-orientation deviation, with respect to said {hkil} plane, in any given point on the major-face collective surface of the plurality of crystal plates is not greater than 0.5°, and such that at least a portion of the major face of each crystal plate is exposed;
• and
• second III-nitride crystal on the major-face collective surface of said undersubstrate, said second III-nitride crystal incorporating and unifying first crystal regions on the exposed areas of the major faces of each crystal plate, and second crystal regions where the first crystal regions merge with each other.