A semiconductor memory device including a memory element for storing data, and a supplemental element substantially electrically associated with the memory element at least at the time of reading data. The semiconductor memory device is for reading data stored in the memory element by applying specified electric action to the compound element including the memory element and the supplemental element substantially electrically mutually associated. The semiconductor memory device is characterized in that the electric characteristic of the supplemental element is adapted to be variable based on a signal for changing the electric characteristic of the supplemental element so that data may be read free from troubles.