Identifying the Diffusion and Drift Conduction Regions in MOSFETs Through $S$ -Parameters

A method for characterizing low-voltage-operating MOSFETs through small-signal S-parameters is introduced. The method allows extracting the drain-to-source channel resistance at zero drain-to-source voltage, which is not feasible with dc conventional methods. Furthermore, this zero drain-to-source voltage RF method identifies the gate voltage where the diffusion and drift conduction mechanisms overlap. This is really helpful in defining the appropriate subthreshold drain current model and its corresponding impact at RF operating conditions. The proposed experimental RF method is validated and compared with a dc-based method for an 80-nm-channel-length nMOSFET.