A versatile stacked storage capacitor on FLOTOX cell for megabit NVRAM's

A versatile stacked storage capacitor on FLOTOX (SCF) structure is proposed for a megabit nonvolatile DRAM (NV-DRAM) cell that has all the features required for NVRAMs. The SCF structure realizes a 30.94- mu m/sup 2/ NV-DRAM cell with 0.8- mu m design rules and allows an innovative flash store/recall (DRAM to EEPROM/EEPROM to DRAM) operation that does not disturb original data in DRAM or EEPROM. This store operation is completed in less than 10 ms. The single cell shows excellent reliability such as store endurance greater than 10/sup 6/ cycles and EEPROM data retention in excess of 10 years under high storage temperatures of 150 degrees C and DRAM write operation at 85 degrees C. The SCF cell has been successfully implemented into the 1 Mb NVRAM.<
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