Annealed wafers having reduced residual voids after annealing and reduced deterioration of TDDB characteristics of an oxide film formed on the annealed wafer, while extending the range of nitrogen concentration contained in a silicon single crystal, are prepared by a method wherein crystal pulling conditions are controlled such that a ratio V/G between a crystal pulling rate V and an average axial temperature gradient G is ≧0.9×(V/G)crit and ≦2.5×(V/G)crit, and hydrogen partial pressure is ≧3 Pa and ≦40 Pa. The silicon single crystal has a nitrogen concentration of >5×1014 atoms/cm3 and ≦6×1015atoms/cm3, a carbon concentration of ≧1×1015 atoms/cm3 and ≦9×1015 atoms/cm3, and heat treatment is performed in a noble gas atmosphere having an impurity concentration of ≦5 ppma, or in a non-oxidizing atmosphere.