A New Cell-Type String Select Transistor in NAND Flash Memories for under 20nm Node

A new string structure, having a cell-type string select transistor line (CT-SSL) is proposed for NAND flash memories beyond 20nm node device. The boosted potentials at a program-inhibited active line were measured with the CT-SSL and compared with the potential measured with a conventional SSL at 4Xnm, 2Xnm, and 1Xnm node devices. The boosted channel potentials were not degraded by drain-induced-barrier-lowering (DIBL) even when using one cell WL as a SSL. As-dopant diffused length by source/drain N+ implantation (S/D N+ IIP) was simulated to determine the minimum required gate length of a SSL. The newly proposed CT-SSL can successfully replace the conventional SSL.