Provided is a flash memory device including a gate structure on a substrate. The flash memory device includes a charge supply layer including a ZnO based material formed between a substrate and a gate structure or formed on the gate structure. Accordingly, the flash memory device can be formed to be of a bottom gate type or of a top gate type by including the charge supply layer. Also, the flash memory device may be realized to be any of a charge trap type and a floating gate type.