An advanced MNOS memory device for highly-integrated byte-erasable 5V-only EEPROMs

An advanced MNOS memory device promising the next-stage, high-density, byte-erasable, 5V-only EEPROM is described. The advanced device features: (1) dimensions that, except for an ultrathin oxide thickness, are reduced in proportion to program voltage, (2) a high drain breakdown voltage obtained by a newly developed high voltage structure with n and n+ drain regions and thick oxide over the n regions. This structure is free from any decrease in program inhibiting voltage or internally boosted voltage that causes serious problems in reliability. The feasibility of shrunk MNOS devices is strongly confirmed in LSI levels, as well as in discrete MNOS devices, by testing not only discrete devices but also low-program-voltage versions of the 16K-bit EEPROM incorporating shrunk MNOS devices. A 20V breakdown voltage is obtained in high-voltage-structure MNOS devices. This is about 10V greater than that of fully self-aligned-structure MNOS devices.