p-type wells are provided within an n-type embedded well of a semiconductor substrate lying in an area for forming a flash memory, in a state of being isolated from one another. A capacitance section, a data write/erase charge injection/discharge section and a data read MIS.cndot.FET are disposed in each of the p-type wells. The capacitance section is disposed between the data write/erase charge injection/discharge section and the data read MIS.cndot.FET. In the data write/erase charge injection/discharge section, writing and erasing of data by an FN tunnel current at a channel entire surface are performed.