A new approach to RF small-signal modeling of MOSFETs

In this paper, we present a new approach to obtain the RF small-signal parameters of MOSFETs, by developing region-wise (strong- and weak-inversion) physics-based small-signal models for the intrinsic part of the device, and eventually coupling them over the moderate inversion region through the use of an interpolation function. The basic premise of this approach is the fact that there is a large difference between the magnitudes of the depletion and inversion charge densities in strong- and weak-inversion regions. The expressions for the Y-parameters are obtained in a power series form, truncated up to the second-order, which is enough to retain sufficient accuracy. Since only the intrinsic parameters are not sufficient to predict the high frequency behavior of short-channel devices, hence, extrinsic parameters are coupled with their intrinsic counterparts in order to obtain the total values of the Y-parameters for the complete device. The results of our model show a sufficiently good match with the TCAD simulations. Also, the continuity of the various device capacitances at a frequency of 50 GHz over the entire range of gate bias validates our model. (paper)