Unified Modeling of Multigate MOSFETs Based on Isomorphic Modeling Principles

T.A. Fjeldly, U. Monga
Norwegian University of Science and Technology, NO

Keywords: ultigate MOSFETs, device modeling, drain current, capacitances


A compact, unified and analytical model is presented for the 3D electrostatics of nanoscale, multigate MOSFETs. The model is based on solutions of the 3D Laplace equation (subthreshold) and Poisson’s equation (above threshold), where suitable 2D isomorphic modeling functions are utilized to describe the potential distribution in the transverse (x,y) cross sections. Here we emphasize the strong inversion modeling. The symmetry between the x and y axes allows us, using the 3D Poisson’s equation, to express the potential along these directions in terms of the center potential. The resulting 1D solutions have a similar form to that of the DG MOSFET. From this, we construct a complete 2D solution for the silicon (x,y) cross sections. Based on this, the device capacitances and the drain current can be calculated in the full range of bias voltages. The model compares well with numerical calculations obtained from the ATLAS device simulator. This unified model covers square gate, double gate, trigate and FinFET devices.