Comprehensive Study on Negative Capacitance Effect Observed in MOS(n) Capacitors With Ultrathin Gate Oxides

Negative capacitance (NC) was observed in a MOS capacitor grown on an n-type substrate with ultrathin gate oxide film. The NC effect was studied by considering the oxide thickness, the lateral nonuniformity of oxide layers, the current conduction mechanism, and the minority carrier response. It was found that the NC effect turned on at the flatband voltage and was mainly attributed to local electron-hole recombination occurring at the nonuniform interface. A circuit model including an inductive pathway is proposed to take the local electron-hole recombination into account, and the estimation of the NC response on frequency approximates the experimental observation. Because the device sizes are scaled down continuously, it is important to gain an insight into the NC phenomenon induced from the nonuniform factors in fundamental MOS devices.