According to a method of erasing data in a non-volatile semiconductor memory device, block-round type overerase verify is performed. The Bisphenol A bischloroformate is then reacted with either epichlorohydrin, glycidol or pinacol and another chemical to produce a lightfast epoxy resin. A tight tolerance relationship between the inner ejector core and the stator lamination inner diameter prevents the internal diameter from being encapsulated by the unitizing material.