Analytical modeling of quantization and volume inversion in thin Si-film DG MOSFETs

A compact physics-based quantum-effects model for symmetrical double-gate (DG) MOSFETs of arbitrary Si-film thickness is developed and demonstrated. The model, based on the quantum-mechanical variational approach, not only accounts for the thin Si-film thickness dependence but also takes into account the gate-gate charge coupling and the electric field dependence; it can be used for FDSOI MOSFETs as well. The analytical solutions, verified via results obtained from self-consistent numerical solutions of the Poisson and Schrodinger equations, provide good physical insight with regard to the quantization and volume inversion due to carrier confinement, which is governed by the Si-film thickness and/or the transverse electric field. A design criterion for achieving beneficial volume-inversion operation in DG devices is quantitatively defined for the first time. Furthermore, the utility of the model for aiding optimal DG device design, including exploitation of the volume-inversion benefit to carrier mobility, is exemplified.