Fully depleted double-gate MSDRAM cell with additional nonvolatile functionality

We demonstrate a new fully depleted (FD) double-gate (DG) MSDRAM cell, which features SONOS type storage node at the back-gate (control-gate). This single-transistor cell, based on the meta-stable dip (MSD) hysteresis effect, can also be operated in non-volatile memory (NVM) mode. The NVM functionality is achieved by Fowler-Nordheim tunneling hole injection into the nitride storage node; the injected holes induce a permanent inversion layer in silicon body. The proposed device shows a large current ratio between '1' and '0' states (similar to 10(3)) and a wide memory window (similar to 3 V). The effect of the NVM functionality on the MSD hysteresis was investigated and combined with the effect of the control-gate bias. The SONOS charging can be used for replacing the second gate (i.e. enabling single-gate MSDRAM) or for achieving 'unified' memory operation. (C) 2011 Elsevier Ltd. All rights reserved.