Patent ID: 7367865

Claim:
A crystalline wafer substrate for an electronic semiconductor element, wherein said crystalline wafer substrate consists of a single crystal, said single crystal consists of sapphire or silicon carbide, said single crystal has at least one active surface, said at least one active surface has a pit density of less than 500 pits/cm 2, and said crystalline wafer substrate having said at least one active surface with said pit density less than 500 pits/cm 2 is obtained by a method comprising the steps of: a) polishing by a polishing means said at least one active surface of said crystalline wafer substrate in order to smooth said at least one active surface; and b) during the polishing changing a polishing direction of a polishing tool performing the polishing over said at least one active surface so that each site or location on the at least one active surface is polished with polishing motions of the polishing tool distributed statistically and uniformly over a 360° angle.