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 equal or greater than 50% relative to total voids; a V1 region having a void density of over 2104/cm3 and below 1105/cm3 is equal or less than 20% of the total area of wafer; a V2 region having a void density of 5102 to 2104/cm3 occupies equal or greater than 80% of the total area of the wafer; and bulk microdefect density is equal or greater than 5108/cm3.