Silicon wafers having excellent voltage resistance characteristics of an oxide film and high C-mode characteristics are derived from single crystal silicon ingots doped with nitrogen and hydrogen, characterized in that a plurality of voids constituting a bubble-like void aggregates are present ≧50% relative to total voids; a V1 region having a void density of over 2×104/cm3 and below 1×105/cm3 is ≦20% of the total area of wafer; a V2 region having a void density of 5×102 to 2×104/cm3 occupies ≧80% of the total area of the wafer; and bulk microdefect density is ≧5×108/cm3.