A semiconductor having an internal memory of the present invention comprises a first memory copying and holding a data held in a storage device; a second memory holding a check code of the data held in the first memory, and being constantly supplied with a source voltage not lower than a data-holding-guarantee voltage; a data check unit detecting error in the data held by the first memory based on the check code; and reloading units copying only the data corresponded to the block having a data error detected therein by the data check unit, from the storage device to the first memory, to make it possible to detect any error in the data held in the first memory to thereby guarantee the data, and to lower the source voltage to be supplied to the first memory.