When a control circuit has received a first erase command, the control circuit controls performing a first pre-write process to allow a first storage device and a second storage device to have threshold voltages, respectively, both increased, and the control circuit thereafter controls performing an erase process to allow the first storage device and the second storage device to have their respective threshold voltages both decreased to be smaller than a prescribed erase verify level. When the control circuit has received a second erase command, the control circuit controls performing a second pre-write process to allow one of the first storage device and the second storage device to have its threshold voltage increased, and control circuit subsequently controls performing the erase process.

Systems, apparatuses and methods may provide for identifying a target sub-block of NAND strings to be partially or wholly erased in memory and triggering a leakage current condition in one or more target select gate drain-side (SGD) devices associated with the target sub-block. Additionally, the leakage current condition may be inhibited in one or more remaining SGD devices associated with remaining sub-blocks of NAND strings in the memory. In one example, triggering the leakage current condition in the one or more target SGD devices includes setting a gate voltage of the one or more target SGD devices to a value that generates a reverse voltage that exceeds a threshold corresponding to the leakage current condition.

An erasing method of a nonvolatile semiconductor memory device of the disclosure includes erasing data of a selected memory cell (step S100); immediately applying a programming voltage lower than a programming voltage in a programming time to all control gates of the selected memory cell after the erasing step, thereby performing a week programming (step S110); performing a erasing verification of the selected memory cell (step S120).

An erasing method of a memory device includes the following steps. It is determined whether a memory passes the first erasing verification operation according to the first erasing verification threshold. When the memory does not pass the first erasing verification operation, an erasing operation is performed on the memory. When the memory passes the first erasing verification operation, a flag is generated and it is determined whether the memory passes a second erasing verification operation according to the second erasing verification threshold. When the memory does not pass the second erasing verification operation, the erasing operation is performed on the memory. When the memory passes the second erasing verification operation, an over-erase correction is performed on the memory. It is determined whether there is a flag indicating that all addresses pass the first erasing verification to determine whether the memory passes the first or second erasing verification operation.

In an example method of operating a nonvolatile memory device, an erase command and a block address designating a target memory block from a plurality of memory blocks are received. Whether the target memory block is an open block including at least one erased word-line is determined based on the erase command and the block address. A pre-program voltage having a first voltage level is applied to word-lines of the target memory block during pre-program period of a erase loop based on the target memory block being a closed block including only programmed word-lines. A pre-program voltage having a second voltage level greater than the first voltage level is applied to a portion of a region, including the at least one erased word-line, of the target memory block during the pre-program period based on the target memory block being the open block.