US Patent 7466592 Semiconductor memory device

A multi-level semiconductor memory device for storing multi-level data having three or more values is implemented by utilizing a nonvolatile memory device for storing 2-valued data. Identification of successive 16-bit data externally applied is performed with external address bit AA [2], and a storage block is selected with external address bit AA [23]. Upper word data LW and lower word data UW are compressed into byte data of 8 bits, respectively, and stored in a memory cell array.