A non-volatile electrically erasable programmable read only memory (EEPROM) capable of storing two bit of information having a nonconducting charge trapping dielectric, such as silicon nitride, sandwiched between two silicon dioxide layers acting as electrical insulators is disclosed. A left and a right...http://www.google.de/patents/US7116577?utm_source=gb-gplus-sharePatent US7116577 - Two bit non-volatile electrically erasable and programmable semiconductor memory cell utilizing asymmetrical charge trapping
