1 K-bit nonvolatile semiconductor read/write RAM

A 1024-bit nonvolatile semiconductor read/write random access memory (RAM) is described which is operated as a static RAM under a stable power supply, and the stored information can be transferred into MNOS memory transistors for nonvolatile storage when the power supply is turned off. A nonvolatile flip-flop cell consisting of 8 MOS transistors and 2 MNOS transistors is used on the basis of p-channel silicon gate technology. The chip size is 4.36 × 5.50 mm². Typical read access time is 900 ns, and the stored data can last for more than one year. Endurable power on and off cycles are 10⁵cycles.