Unified Scale Length for Four-Terminal Double-Gate MOSFETs

A unified scale length formula for four-terminal double-gate (DG) MOSFETs is proposed in this paper to provide a guideline for device design to obtain a practical threshold voltage and a subthreshold swing. By investigating the boundary conditions for Laplace's equation in the channel of DG MOSFETs, the evanescent-mode analysis method is extended to form a unified scaling scheme. The unified model is proved to be applicable to two common device structures: ultrathin-body silicon-on-insulator and symmetric DG MOSFETs based on 2-D technology computer-aided design simulation. With this model, the relationship among different well-known scaling rules can be well explained and understood.