A Charge-Based Large-Signal Model for Thin-Film SOI MOSFET's

A charge-based large-signal model for thin-film SOI(Si-on-SiO/sub 2/) MOSFET's, intended for computer simulation of transient characteristics of SOI and 3-D circuits, is developed emphasizing the structural uniqueness of the devices. Closed-form expressions for the quasi-static terminal charges, simpler than those for the bulk MOSFET because of the thin-film structure, are derived in terms of terminal voltages and device parameters, and are used to define the terminal currents. Equivalent circuits, developed from the charge-based model, show that the device can be accurately represented using only real reciprocal capacitances by explicitly accounting for the transient channel transport current I/sub TT/. The analytic expression for I/sub TT/, obtainable for the thin-film structure, enables the evaluation of the finite-carrier transit delay in the channel and of the corresponding charge nonconservation in the conventional reciprocal-capacitance MOSFET model that does not account for the delay.