Threshold Voltage Modeling of Double Gate-All-Around Metal-Oxide-Semiconductor Field-Effect-Transistors (DGAA MOSFETs) Including the Fringing Field Effects

In this paper, an analytical threshold voltage model of double gate-all-around metal-oxide-semiconductorfield-effect-transistors (DGAA MOSFETs) including the fringing field effects is developed. The total fringing capacitance arising due to induced fringing fields in the device is divided into inner, outer and bottom fringing capacitance. A simple expression for each fringe capacitance is developed individually. The 3-D Poisson's equation has been solved in the channel region using the parabolic potential approximation method to develop the surface potential expressions. The effects of fringing capacitances of inner and outer gates which causes charge induction in the source/drain regions have been incorporated within the developed surface potential expressions. The change in potential due to these induced charges of source/drain region along the channel is formulated and added with the developed surface potential expression at both surfaces. The obtained modified surface potential equations have been utilized to derive the expression of the threshold voltage of the device. The performance of the proposed model has been compared with the previously developed model of DGAA MOSFET structure without High- k dielectrics. The effects of variation of device parameters on the threshold voltage have been also analyzed. The accuracy of the proposed model has been verified by numerical simulation results obtained by a device simulator VTCAD from Cogenda Int.