A memory wherein the bit reliability of the memory cells can be dynamically varied depending on the application or the memory status, the operation stability is ensured, and thereby a low power consumption and a high reliability are realized. Either a mode (a 1-bit/1-cell mode) in which one bit is composed of one memory cell or a mode (a 1-bit/n-cell mode) in which one bit is composed of n (n is two or more) connected memory cells is dynamically selected. When the 1-bit/n-cell mode is selected, the read/write stability of one bit is enhanced, the cell current during read is increased (read is speeded up), and a bit error, if occurs, is self-corrected. Especially, a pair of CMOS transistors and a control line for performing control so as to permit the CMOS transistors to conduct are added between the data holding nodes of n adjacent memory cells. With this, the word line (WL) is controlled, and thereby the operation stability is further improved.