Nonvolatile reversible capacitance changes through filament formation in a floating-gate metal-oxide-semiconductor capacitor with Ag/CeOx/Pt/HfOx/n-Si structure

Nonvolatile and reversible capacitance changes are demonstrated in a floating-gate metal-oxide-semiconductor (FG-MOS) capacitor with a Ag-control-gate/CeOx-control-oxide/Pt-floating-gate/HfOx-tunneling-oxide/n-Si structure. Different from the conventional floating-gate MOS field-effect-transistor (MOSFET) operating with a threshold voltage shift by electrical charging in the floating-gate (charge storage node), the proposed device operates with the change of gate oxide capacitance as one of the parameters determining the electrical properties of MOSFET. Applying positive voltage to the Ag control-gate forms a conducting filament in the Ag/CeOx/Pt stack and consequently increases the gate oxide capacitance. The accumulation capacitance increases from the capacitance of serial capacitors consisting of Ag/CeOx/Pt and Pt/HfOx/n-Si before the filament formation to that of a single capacitor of Pt/HfOx/n-Si after the filament formation. The capacitance is reversibly decreased to the initial value by rupturing the filament upon applying negative voltage. The change of capacitance is stable over time with the retention >90% for 12 h of measured time. These noncharge-storage-based nonvolatile and reversible changes in the gate oxide capacitance through the filament formation would modulate the MOSFET properties with the advantages of better uniformity, superior immunity to the radiation, and less cross talk between adjacent devices for the application to nonvolatile memory and programmable logic devices.