A non-volatile semiconductor memory device includes: a memory cell section having a plurality of memory cells, each of the memory cells including a flash cell section and a DRAM capacitor section, the flash cell section having at least a drain, a source and a floating gate, the drain being connected to a bit line, the DRAM capacitor section having a capacitive element with two electrodes, one of the electrodes being connected to the source, and the other one of the electrodes being connected to a power supply terminal, and the memory cell being constructed in such a manner that electrons are injected into and extracted from the floating gate at least through the drain by a tunnel current; a register section connected to the memory cell section through the bit line; a bit line selector into which a signal from the bit line is input; and a sensing amplifier for receiving an output from the bit line selector as an input signal. According to the present invention, in the normal operation mode, it is possible to achieve a high-speed random access similar to the one in a general DRAM by reading out or rewriting the volatile data stored in the capacitive element section. On the other hand, in the data retaining mode, final information or invariable information can be stored in the non-volatile memory cell section as non-volatile data.