US Patent 7230853 Selective erase method for flash memory

Selective erase method for a flash memory device including a group of memory cells arranged in rows and columns include performing an erase operation on the group of memory cells and verifying the erase operation on the group of memory cells to determine threshold voltages of the memory cells. At least one row of memory cells including memory cells having a threshold voltage lower than a desired erase threshold voltage is identified. A further erase operation is performed on the group of memory cells excluding memory cells of the at least one row of memory cells including memory cells having a threshold voltage lower than a desired erase threshold voltage.