Method of erasing NAND flash memory device

1. A method of erasing data stored in a NAND flash memory device including a plurality of cell block having a plurality of cell string, and a plurality of X-decoder constructed of a plurality of high voltage transistors, the method comprising:

applying a leakage protection voltage is applied to a well of the high voltage transistors in the X-decoder during an erasing operation for removing data of one of the cell blocks.

2. The method according to claim 1 , wherein the leakage protection voltage is in the range of −0.1˜−1.0 V.

3. A method of erasing data stored in a NAND flash memory device including plural cell blocks each having cell strings, bit lines, word lines, string selection transistors connected between the cell strings and the bit lines, and ground selection transistors connected between the cell strings and a common ground line, and plural X-decoders each having gate string selection high voltage transistors for applying predetermined gate voltages to the string selection transistors, the ground selection transistors, and gate terminals of the memory cells, gate ground selection high voltage transistors, and cell gating high voltage transistors, the method comprising:

selecting one of the cell blocks for an erasing operation;

applying a power supply voltage to gate terminals of the gate string selection high voltage transistor, the gate ground selection high voltage transistor, and the cell gating high voltage transistor in the X-decoder coupled to the selected cell block, applying a leakage protection voltage to a well of the high voltage transistors, and applying a floating voltage to drain terminals of the gate string selection high voltage transistor and the gate ground selection transistor;

applying a ground voltage to a drain terminal of the cell gating high voltage transistor, gate terminals of the gate string selection high voltage transistor, the gate ground selection high voltage transistor, and the cell gating high voltage transistor, of the X-decoder coupled to a deselected cell block, and applying a leakage protection voltage to the well; and

applying an erasing voltage to the well of the plural cell blocks.

4. The method according to claim 3 , wherein the leakage protection voltage is in the range of −0.1˜−1.0 V.

5. The method according to claim 3 , wherein the floating voltage is in the range of 3.5˜5.5 V while the erasing voltage is in the range of 20˜22 V.