The dynamics of the threshold voltage calculation is evaluated for the tri-gate architecture of device. The 3-D poisson's equation with eight boundary conditions is solved analytically and an analytical threshold model for tri-gate Si MOSFET device is developed. TCAD simulation result of the same device structure is also presented and it agrees well with our threshold analytical model. Furthermore, this analytical threshold model is capable of doing rudimentary first order comparisons of the threshold voltage with respect to device dimensions and semiconductor material type. (C) 2007 Elsevier Ltd. All rights reserved.