FinFETs with ONO BOX for multi-bit unified memory

Advanced FinFETs are fabricated on the ONO buried insulator.The nitride buried insulator can trap charges for the flash memory operation.The same device was investigated for the 1T-DRAM operation.By combining nonvolatile and volatile, multi-bit 1T-DRAM operation was obtained.Analog/logic and memory operation can be performed at the same cell. Floating-body-induced transient phenomena in advanced FinFETs fabricated on SOI with SiO2-Si3N4-SiO2 (ONO) buried insulator were studied for unified memory with multi-bit capability. The nitride layer can store nonvolatile charges by applying back-gate or drain bias. The trapped/detrapped charges in the nitride layer are sensed remotely, by gate coupling, through the variation of the drain current flowing at the front-channel. On the other hand, the transistor silicon body can accommodate volatile charges (generated by impact ionization) that also modify the drain current. Our experiments demonstrate that these two memory modes can be advantageously combined for multi-bit unified memory operation.