Modeling of ultrathin double-gate nMOS/SOI transistors

An analytical model valid near and below threshold is derived for double-gate nMOS/SOI devices. The model is based on Poisson´s equation, containing both the doping impurity charges and the electron concentration. An original assumption of the constant difference between surface and mid-film potentials is successfully introduced. The model provides explicit expressions of the threshold voltage and threshold surface potential, which may no longer be assumed to be pinned at the limit of strong inversion, and demonstrates the nearly ideal subthreshold slope of ultrathin double-gate SOI transistors. Very good agreement with numerical simulations is observed. Throughout the paper we give an insight into weak inversion mechanisms occurring in thin double-gate structures