A flash memory device includes first and second memory cell array blocks and a row decoder coupled to the first memory cell array block and the second memory cell array block. The row decoder includes a block decoder, a single high voltage level shifter that is coupled to both the first and second memory cell array blocks, the single high voltage level shifter configured to provide a block wordline signal of a high voltage to the first and second memory array blocks in response to a block selection signal received from the block decoder, a first pass transistor unit, and a second pass transistor unit.