An epitaxial semiconductor wafer having a wafer substrate made of semiconductor single crystal, an epitaxial layer deposited on a top surface of said wafer substrate and a polysilicon layer deposited on a back surface of said wafer substrate. The semiconductor single crystal is exposed in a region defined within a distance of at least 50 m from a ridge line as a center, which is defined as an intersection line between said back surface and a bevel face interconnecting said top surface and said back surface of said wafer substrate. The polysilicon layer is 1.0 to 2.0 m thick. The epitaxial layer is 1.0 to 20 m thick. The wafer substrate is a silicon single crystal.