The compact modeling of nanowire MOSFETs (also called surrounding gate MOSFETs or Gate All Around MOSFETs) is a hot topic. The first compact drain current models were published in 2004:
Researchers are now addressing the compact modeling of charges and capacitances. In January 2007, in IEEE Transactions on Electron Devices, the first compact model for charges and capacitances of surrounding gate MOSFETs was published: Analytical Charge and Capacitance Models of Undoped Cylindrical Surrounding-Gate MOSFETs, by Moldovan O., Jiménez D., Roig J. and Iñiguez B.
In March 2007, a new charge model for surrounding gate MOSFETs has been published in IEEE Transactions on Electron Devices: Analytic Charge Model for Surrounding-Gate MOSFETs, by Yu B., Lu W.-Y., Lu H. and Taur, Y.
Both models are based on the electrostatic potential soultion obtained by D. Jimenez et al. (Continuous analytic I-V model for surrounding-gate MOSFETs, IEEE Electron Device Letters, August 2005)
from the 1-D Poisson's equation in the radial direction (neglecting the effect of the lateral field). B. yu et al use the initial formulation proposed by Jimenez; charge and capacitances are written in terms of a variable which depends on the surface potential, and is calculated iteratively at the source and drain ends of the channel. Moldovan uses a charge-based formulation: from a charge control model, developed by B. Iñiguez et al. (Explicit continuous model for long-channel undoped surrounding gate MOSFETs, IEEE Transactions on Electron Devices, August 2005)
from the analysis of D. Jimenez et al, analytical expressions of charges and capacitances are obtained in terms of the mobile charge sheet densities at the source and drain ends of the channel; explicit expressions of the mobile charge sheet denisities are finally used.