A semiconductor device includes: a first sector (12) having data that are all to be erased and having flash memory cells; a second sector (14) having data that are all to be retained and having flash memory cells; a sector select circuit (16) selecting a pair of sectors from among sectors during erasing the data in the first sector, said pair of sectors being the first sector and the second sector; and an SRAM array (storage) (30) retaining the data of the second sector. The present invention can provide a semiconductor device in which a reduced number of sector select circuits is used so that the area of memory cell array can be reduced and provide a method of controlling the semiconductor device.