Nonvolatile memory device and read method thereof

1. A nonvolatile memory device comprising:

a memory cell array connected to a plurality of word lines; and

a voltage generator for supplying a select read voltage to a select word line and an unselect read voltage to an unselect word line among the plurality of word lines when a read operation is performed,

wherein the voltage generator generates the unselect read voltage having different level according to whether the unselect word line is adjacent to the select word line or not; and

wherein the voltage generator supplies an unselect read voltage to at least one between an upper word line and a lower word line adjacent to the select word line when a threshold voltage of a select memory cell connected to the select word line is decreased, the unselect read voltage being lower than unselect read voltages supplied to other unselect word lines.

2. A nonvolatile memory device comprising:

a memory cell array connected to a plurality of word lines; and

a voltage generator for supplying a select read voltage to a select word line and an unselect read voltage to an unselect word line among the plurality of word lines when a read operation is performed,

wherein the voltage generator generates the unselect read voltage having different level according to whether the unselect word line is adjacent to the select word line or not; and

wherein the voltage generator supplies an unselect read voltage to at least one between an upper word line and a lower word line adjacent to the select word line when a threshold voltage of a select memory cell connected to the select word line is increased, the unselect read voltage being higher than unselect read voltages supplied to other unselect word lines.

3. A read method of a nonvolatile memory device, comprising:

performing a first read operation by supplying a select read voltage to a select word line and supplying an unselect read voltage to an unselect word line;

detecting whether an error occurs in the first read operation or not; and

performing a second read operation by changing a voltage of a word line adjacent to the select word line when an error occurs in the first read operation.

4. The read method of claim 3 , wherein the voltage generator supplies an unselect read voltage to at least one between an upper word line and a lower word line adjacent to the select word line when a threshold voltage of a select memory cell connected to the select word line is decreased, the unselect read voltage being lower than unselect read voltages supplied to other unselect word lines.

5. The read method of claim 3 , wherein the voltage generator supplies an unselect read voltage to at least one between an upper word line and a lower word line adjacent to the select word line when a threshold voltage of a select memory cell connected to the select word line is increased, the unselect read voltage being higher than unselect read voltages supplied to other unselect word lines.

6. The read method of claim 3 , wherein whether an error occurs in the first read operation or not is detected by an error correction circuit.

7. The read method of claim 3 , further comprising performing the second read operation by changing the select read voltage supplied to the select word line when an error occurs in the first read operation.

8. The read method of claim 3 , further comprising performing a third read operation by changing the select read voltage supplied to the select word line when an error occurs in the second read operation.

9. The read method of claim 3 , further comprising:

detecting whether the number of changing a voltage of a word line adjacent to the select word line exceeds the reference count or not when an error occurs in the second read operation; and

performing a third read operation by changing the select read voltage supplied to the select word line when the number of changing a voltage of a word line adjacent to the select word line exceeds the reference count.

10. A read method of a nonvolatile memory device, comprising:

performing a read operation by supplying a select read voltage to a monitoring word line and supplying an unselect read voltage to an unselect word line;

detecting whether data stored in a monitoring cell connected to the monitoring word line is normally readout or not; and

performing a read operation on the monitoring cell again by changing a voltage of a word line adjacent to the monitoring word line when data stored in the monitoring cell is not normally readout.

11. The read method of claim 10 , further comprising performing a read operation on a select memory cell by supplying a voltage to a word line adjacent to a select word line when data stored in the monitoring cell is normally readout, the voltage having the same level as the voltage of the word line adjacent to the monitoring word line.

12. The read method of claim 10 , further comprising performing a read operation on the monitoring cell by changing the select read voltage supplied to the monitoring word line when data stored in the monitoring cell is not normally readout and the number of changing the voltage of the word line adjacent to the monitoring word line exceeds the reference count.