NONVOLATILE MEMORY DEVICE, MEMORY SYSTEM INCLUDING THE SAME, AND METHOD OF OPERATING NONVOLATILE MEMORY DEVICE

A non-volatile memory device includes a non-volatile memory cell array including a plurality of word lines, a voltage generator configured to generate a first high-voltage using a supply voltage and a second high-voltage using an external voltage which is higher than the supply voltage, and a word line selection circuit configured. The word line selection circuit is configured apply, during a program operation of the memory cell array, the first high-voltage to a selected word line among the plurality of word lines, and the second high-voltage to unselected word lines among the plurality of word lines