Two-bit/cell characteristics of silicon-oxide-nitride-oxide-silicon flash memory devices with recessed channel structure

We proposed a device structure for novel 2-bit/cell silicon-oxide-nitride-oxide-silicon (SONOS) flash memory and characterized the device for sub-50 nm non-volatile memory (NVM) technology. The proposed memory cell has a nitride layer formed on the surface of the recessed channel reuion for a charge storage node. The threshold voltage window of similar to 3 V was achieved by hot carrier injection under a V(GS) of 5 V and a V(DS) of 3.5 V for programming. It was shown that counter channel doping near the bottom of the recessed channel is very important and can improve the V(th) margin for 2-bit/cell operation by similar to 4 times. By controlling doping profiles of the p-type channel doping and the n-type counter channel doping in the recessed channel region, we could obtain the V(th), margin more than similar to 2 V. Moreover, for a bit-programmed cell, reasonable bit-erasing characteristics were also shown.