An epitaxial silicon wafer cut from a silicon single crystal grown by the Czochralski method, and having a diameter of 300 mm or more. In this epitaxial silicon wafer, the time required to cool every part of the silicon single crystal during the growth from 800° C. down to 600° C. is set to 450 minutes or less, the interstitial oxygen concentration is from 1.5×1018 to 2.2×1018 atoms/cm3 (old ASTM standard), the entire surface of the cut silicon wafer is composed of a COP region, and the BMD density in the bulk of the epitaxial wafer after a heat treatment at 1000° C. for 16 hours is 1×104/cm2 or less. In this epitaxial silicon wafer, even if the thermal process in a semiconductor device fabrication process is a low temperature thermal process, epitaxial defects do not occur, as well as sufficient gettering capability being obtainable.