The modeling of MOS transistors for integrated circuit design has been driven by the needs of digital circuit simulation for many years. The trend toward mixed analog-digital chips creates a necessity for MOSFET models appropriate for analog and RF design [1]. Strong inversion used to be the prevailing MOS operation region, but as a consequence of the technological trend toward shorter channel lengths, off-state leakage constraints, and reduced supply voltages, MOS devices now often operate in the moderate and weak inversion regions [2].

Most of the MOSFET models for computer simulation, from the SPICE Level 1 model to BSIM4, have relied on approximate solutions that are only valid in particular regions of operation connected mathematically to provide continuous solutions. Because the threshold of strong inversion V _T is the key parameter in these regional models, they are also called V _T-based models. The regional approach leads to inaccuracy between regions and consequently this class of models is not accurate enough to represent the moderate inversion region [3], widely employed in low supply voltage circuits.

For the above reasons the industry is turning away from V _T-based MOSFET models. The two main approaches as candidates to replace BSIM3-4 models are inversion-charge based and surface-potential based models. This chapter provides an overview of the approaches taken by the developers of this new generation of models. A summary of the fundamental properties of advanced MOSFET models is presented in [4], a joint paper written by the developers of the main...