Analytical modelling of Multiple-gate MOSFETs

In this work, the interface coupling in short-channel Multiple-gate MOSFETs (MuGFETs) structures is modelled. Based on the solution of the 3D Laplace's equation, the short-channel subthreshold characteristics (Subthreshold current, Subthreshold Slope, Roll-off and DIBL) are calculated and compared to experimental data with an excellent agreement, and without the need of any fitting parameters. The model has been extended to the total drain-current characteristics with the use of smoothing functions. Additionally, the simplification in the case of long channels allows deriving a general threshold voltage valid for all back-gate biases (extension to vertical MuGFETs of the “Lim and Fossum” interface coupling model [1]). Additionally, it is demonstrated that experimental fully depleted devices can operate in the ‘back-interface inversion’ regime even at VG2 grounded. As a result, two threshold voltages appear in the transistors.