A memory device comprises a drain select line, a source select line, word lines, and a string connected between a bit line and a common source line. A program-inhibited voltage is applied to the bit line and a first voltage of a positive potential is applied to the drain select line. A second voltage for activating a programmed memory cell is applied to a word line to which the programmed memory cell is connected. A programming operation is performed by applying a program voltage to a selected word line and applying a pass voltage to the unselected word lines.