A semiconductor memory device has a malfunction prevention device and a nonvolatile memory. The nonvolatile memory is a memory cell including: a gate electrode formed on a semiconductor layer via a gate insulating film; a channel region disposed below the gate electrode; diffusion regions disposed on both sides of the channel region and having a conductive type opposite to that of the channel region; and memory functional units formed on both sides of the gate electrode and having a function of retaining charges.