MAS-ROM-electrically reprogrammable ROM with decoder

The electrical characteristics of an MAS-ROM with on-the-chip X-Y matrix decoding and its reliabilities are evaluated. The MOS-ROM makes use of the so-called charge-storage phenomena in the gate insulator film and provides an electrical reprogrammable and nonvolatile integrated-circuit memory device in which one memory cell is composed only of an N-channel enhancement-type MAS transistor. The threshold voltage of the transistor is selectively increased by electron injection from the channel and decreased by the application of high negative voltage to the gate. The reliability test shows that the long-term decay has a logarithmic dependence on time with a slope of 0.7 V per decade of storage time under a gate voltage of +10 V at 150°C.