New challenges in MOS compact modeling for future generation CMOS

As bulk-MOS technology is approaching its fundamental limit, non-classical devices such as multiple-gate (MG) and silicon-nanowire (SiNW) transistors emerge as promising candidates for future generation device building blocks. This trend poses new challenges to developing a compact model suitable for these new device structures and requires a paradigm shift in the core model structure. Conventional bulk-MOS models are based on four-terminal unipolar conduction in a doped channel with ideal symmetrical PN-junction source/drain contacts. In MG/NW MOSFETs, however, the device becomes three-terminal with undoped channel and possible bipolar conduction, and source/drain contacts become an integral part of intrinsic channel. Source/drain asymmetry, either intentional or unintentional, in a theoretically symmetric MOSFET also becomes important to be captured in a compact model, which is nontrivial in a model that depends on terminal source/drain swapping at the circuit level. This paper discusses these new challenges and demonstrates solutions based on the unified regional modeling (URM) approach.