Nonvolatile memory devices and methods of operating the same

Abstract

A nonvolatile memory device includes memory blocks that each include cell strings formed vertically on a substrate. The cell strings are coupled to a plurality of bit-lines. The cell strings each include memory cells connected to a string selection transistor. A method of operating the nonvolatile memory device includes performing an erase operation on a first memory block of the memory blocks in response to an erase command, performing an erase verification operation on the memory cells of the first memory block, performing a first sensing operation on the string selection transistors of each of the cell strings coupled to at least some bit-lines of the first memory block, and determining whether the first memory block is a fail block at least based on a result of the first sensing operation. The first sensing operation is based on a first sensing scheme selected among a plurality of sensing schemes.