A method for preventing generation of program disturbance incurred by hot electrons in a NAND flash memory device. A channel boosting disturb-prevention voltage lower than a program-prohibit voltage applied to other word lines is applied to edge word lines coupled to memory cells that are nearest to select transistors. As a result, an electric field between the memory cells coupled to the edge word lines and the select transistors is weakened, and the energy of the hot electrons is reduced.