Two-Bit/Cell Programming Characteristics of High-Density NOR-Type Flash Memory Device with Recessed Channel Structure and Spacer-Type Nitride Layer

摘要

The structure of novel 2-bit/cell silicon-oxide-nitride-oxide-silicon (SONOS) flash memory device was proposed and characterized for sub-50 nm non-volatile memory (NVM) technology. A proposed memory cell has spacer-type storage nodes on both sidewalls in a recessed channel region. 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 ～2.5 times. By controlling doping profiles of the channel doping and the counter channel doping in the recessed channel region, we could obtain the V_(th) margin more than ～1.5 V.