US Patent 8081501 Multi-level nonvolatile memory device using variable resistive element

A multi-level nonvolatile memory device using variable resistive element with improved reliability of read operations is provided. A multi-level nonvolatile memory device comprises a multi-level memory which includes a resistance element, wherein the resistance level of the resistance element is variable depending on data stored in the multi-level memory cell, and a read circuit which provides the multi level memory cell with a read bias and performs a sensing operation in response to the read bias, wherein the read bias has at least two levels during a read cycle.