Patent ID: 8023330

Claim:
A method of erasing a nonvolatile memory device, the method comprising: performing an erase operation on memory cells of a selected block; performing a dummy soft program operation on the cells on which the erase operation has been performed; performing a first erase verify operation that determines whether a threshold voltage of the memory cells is lower than a first erase verify voltage; repeatedly performing the erase operation and the dummy soft program operation by increasing an erase voltage by a first step voltage until the threshold voltage of the entire memory cells becomes lower than the first erase verify voltage; in the event that the threshold voltage of the entire memory cells becomes lower than the first erase verify voltage, performing a soft program operation; performing a soft program verify operation that determines whether the threshold voltage of the memory cells is higher than a soft program verify voltage; and repeatedly performing the soft program operation by increasing a soft program voltage by a second step voltage until a cell is programmed to have the soft program verify voltage.