Volatile/non-volatile dynamic RAM system

A volatile/non-volatile dynamic field-effect RAM cell having volatile data store, volatile-to-nonvolatile store, and nonvolatile-to-volatile restore capabilities, comprising:

• a semiconductor substrate of a first conductivity type;
• a capacitor formed in said substrate for storing binary information in the form of charge volatilely stored therein;
• means for selectively supplying charge to said volatile capacitor;
• a nonvolatile capacitor formed in said substrate operable for selectively receiving, storing and restoring to the volatile capacitor the binary charge information;
• energy barrier means in said substrate interposed between said volatile capacitor and said nonvolatile capacitor, said energy barrier means providing a predetermined energy barrier to charge transfer from said nonvolatile capacitor to said volatile capacitor;
• and
• wherein said means for supplying charge includes a charge transfer device for effecting the charge storage state of the volatile storage capacitor during volatile operation and cooperating with the nonvolatile capacitor to effect the nonvolatile-to-volatile restore operation.

A volatile/non-volatile dynamic random access memory system having volatile store, volatile-to-nonvolatile store, and nonvolatile-to-volatile restore capabilities, comprising:

• a plurality of volatile/non-volatile dynamic field effect memory cells formed in a substrate;
• each cell comprising a capacitor formed in the substrate for volatilely storing binary charge information;
• non-volatile capacitive charge storage means suitable for effecting charge-pumped restore or charge transfer restore to the volatile capacitor of information stored in said non-volatile charge storage means;
• a transfer gate for controlling the application of binary charge information to the volatile capacitor for volatile storage and to the non-volatile storage means to initiate nonvolatile-to-volatile restore to the volatile capacitor;
• said non-volatile storage means comprising a split gate capacitor section having an alterable threshold, non-volatile section and a non-alterable threshold capacitor section interposed between said non-volatile section and said volatile capacitor;
• said non-alterable capacitor section providing a substrate surface potential barrier for preventing charge leakage from said non-volatile capacitor section to said volatile capacitor during charge-pumped restore operation;
• amplifier means including an output terminal, said amplifier means being connected to said memory cells and being responsive to a voltage stored on said volatile capacitor representing the binary state of said capacitor for generating a signal representing said voltage at said output node;
• and
• means for accessing the signal information at said output node.