Method of performing an erase operation in a non-volatile memory device

A method of performing an erase operation in a non-volatile memory device having a memory cell array which includes at least one blocks having multi level cells, the method comprising:

• shifting every threshold voltage distribution into a threshold voltage distribution having highest level by pre-programming every cell in a block selected for erase;
• performing an erase operation on the pre-programmed memory block;
• performing a soft program and a verifying operation on the memory block;
• dividing the memory block into a first group and a second group in case that the memory block is passed in accordance with the verifying result;
• performing a verifying operation on the first group and the second group, and indicating a flag to a group not passed;
• and
• performing a soft program and a verifying operation on the group to which the flag is indicated.

A method of performing an erase operation in a nonvolatile memory device, the method comprising:

• performing an erase operation on an area of the memory device;
• performing a first soft program operation on the area of the memory device;
• dividing the area of he memory device into a first group and second group;
• and
• performing a second soft program operation on the first group and a third soft program operation on the second group.