First demonstration of diode-type 3-D NAND flash memory string having super-steep switching slope

Super-steep switching is successfully demonstrated using positive feedback (PF) in fabricated diode-type 3-D NAND flash memory strings. Thanks to the PF, the subthreshold swing (SS) measured in a cell of a string during read operation is less than 1 mV/dec at turn-on voltage (Von) regardless of the polarity and the amount of the charge stored in the cell. This string has memory characteristics similar to conventional FET-type string while keeping much better SS than that of the FET-type string even after program/erase (P/E) cycling.