Memory device and method of operating the same

1. A memory device including a plurality of memory blocks, the memory device comprising:

a voltage generator configured to generate voltages used by the memory device in performing an erase operation on a selected memory block among the plurality of memory blocks;

an erase stop controller configured to control stopping and resuming the erase operation, and counting the number of times the erase operation is stopped to generate a stop count value when the erase operation is stopped, wherein when the erase operation is resumed, the erase stop controller is configured to set, based on the stop count value, an offset voltage of voltages to be applied to word lines connected to the selected memory block while performing the erase operation; and

a count value storage configured to store and output the stop count value.

2. The memory device of claim 1 , wherein the count value storage comprises one of volatile memory cells and non-volatile memory cells.

3. The memory device of claim 1 , wherein the erase stop controller is configured to control a peripheral circuit of the memory device to stop the erase operation when the erase stop controller receives one of a program command and a read command from a memory controller while performing the erase operation.

4. The memory device of claim 3 , wherein the erase stop controller is configured to:

maintain the stopped state of the erase operation when the erase stop controller receives one of a new program command and a new read command from the memory controller after the erase operation is stopped; and

stop the erase operation again when the erase stop controller receives one of another program command and another read command from the memory controller after the stopped erase operation is resumed.

5. The memory device of claim 3 , wherein the erase stop controller is configured to:

set the offset voltage to be greater as the stop count value increases; and

set the offset voltage to be less as the stop count value decreases.

6. The memory device of claim 3 , wherein each of the plurality of memory blocks has a three-dimensional structure and the erase stop controller is configured to set the offset voltage differently according to positions of the word lines connected to the selected memory block.

7. The memory device of claim 3 , wherein each of the plurality of memory blocks has a three-dimensional structure and when the word lines connected to the selected memory block are divided into a plurality of groups, the erase stop controller is configured to control the voltage generator to generate a voltage higher than a word line voltage set for each of the plurality of groups by the offset voltage.

8. The memory device of claim 3 , wherein each of the plurality of memory blocks has a three-dimensional structure and when the word lines connected to the selected memory block are included in one group, the erase stop controller is configured to control the voltage generator to generate a voltage higher than the voltage to be applied to the word lines connected to the selected memory block by the offset voltage.

9. The memory device of claim 1 , wherein:

the erase stop controller is configured to output a stop count request, for obtaining the stop count value, to the count value storage so that the erase operation is resumed based on the stop count value after the erase operation is stopped; and

the count value storage is configured to output the stored stop count value as the stop count value in response to the stop count request.

10. A method of operating a memory device including a plurality of memory blocks, the method comprising:

performing an erase operation on a selected memory block among the plurality of memory blocks;

stopping the erase operation when a program command or a read command is received while performing the erase operation;

counting the number of times the erase operation is stopped to generate a stop count value when the erase operation is stopped; and

resuming the erase operation based on the stop count value after an operation corresponding to the program command or the read command is completed, wherein resuming the erase operation comprises setting, based on the stop count value, an offset voltage of voltages to be applied to word lines connected to the selected memory block while performing the erase operation.

11. The method of claim 10 , wherein setting the offset voltage comprises: setting the offset voltage to be greater as the stop count value increases; and setting the offset voltage to be less as the stop count value decreases.

12. The method of claim 10 , wherein setting the offset voltage, when each of the plurality of memory blocks has a three-dimensional structure, comprises setting the offset voltage differently according to positions of the word lines connected to the selected memory block.

13. The method of claim 12 , wherein setting the offset voltage comprises:

setting the offset voltage to be less when the selected memory block is positioned at an upper portion of the three-dimensional structure; and

setting the offset voltage to be greater when the selected memory block is positioned at a lower portion of the three-dimensional structure.

14. The method of claim 12 , wherein setting the offset voltage comprises:

setting the offset voltage to be greater when the selected memory block is positioned at an upper portion of the three-dimensional structure; and

setting the offset voltage to be less when the selected memory block is positioned at a lower portion of the three-dimensional structure.

15. The method of claim 10 , wherein resuming the erase operation, when each of the plurality of memory blocks has a three-dimensional structure and the word lines connected to the selected memory block are divided into a plurality of groups, comprises applying a voltage higher than word line voltage set for each of the plurality of groups by the offset voltage.

16. The method of claim 10 , wherein resuming the erase operation, when each of the plurality of memory blocks has a three-dimensional structure and the word lines connected to the selected memory block are included in one group, comprises applying a voltage higher than the voltage to be applied to the word lines connected to the selected memory block by the offset voltage.

17. The method of claim 10 , further comprising storing the stop count value in volatile memory cells.

18. The method of claim 17 , wherein resuming the erase operation comprises:

outputting a stop count request for obtaining the stop count value stored in the volatile memory cells; and

receiving the stop count value in response to the stop count request.