US Patent 7881106 Nonvolatile semiconductor memory device

A nonvolatile semiconductor memory device includes a nonvolatile memory including a first area which stores data for every n bits (n is a natural number of not less than 2), and a second area which stores data for every 1 bit, each of the first area and the second area including a plurality of memory cells each configured to store n-bit data on the basis of a threshold voltage, and a controller which sets 2n threshold voltages corresponding to n bits when writing n-bit data to a first memory cell included in the first area, and executes the n-bit data write operation when writing 1-bit data to a second memory cell included in the second area.