Memory device and methods of erasure operation using different float times for string selection transistors

Abstract

A memory, a memory system and a method of operating the memory are disclosed, belonging to the field of storage technologies. When an erase operation is performed on various strings in the block of the memory, if there are a first string that has been erased and a second string that has not been erased among the strings, the selection line coupled to the first selection transistor of the first string is floated in advance before the selection line coupled to the first selection transistor of the second string is floated, to thereby reduce the erasing speed of the first string and prevent the first string from being over-erased during the erasing of the second string, which reduces the possibility of lateral spreading of memory cells in the subsequent first string after programming, and weakens the threshold voltage drift of the memory cells in the first string.