1. A semiconductor memory device, comprising: a memory cell array including a plurality of memory cells, each memory cell configured to store plural bits of data; and a controller configured to execute a write operation on the memory cells such that user data are written in at least one of the plural bits of data and prescribed data are written in the remaining bits of the plural bits of data, wherein the number of bits of user data stored in the memory cells is less than the number of plural bits of data that each memory cell is configured to store.