A new decoupled C-V method is proposed to deter- mine the intrinsic (effective) channel region and extrinsic overlap region for miniaturized MOSFET’s. In this approach, a unique channel-length-independent extrinsic overlap region is extracted at a critical gate bias, so bias-independent effective channel lengths (Zeff) are achieved. Futhermore, the two-dimensional (2D) charge sharing effect is separated from the effective channel region. Based on this Zeff and the associated bias-dependent channel mobility, µeff, the drain-and- source series resistance (RDs) can be derived from the I-V characteristics for each device individually. For the first time, the assumption or approximation for rdsand µeffcan be avoided, thus the difficulties and controversy encountered in the conventional I-V method can be solved. The 2D charge sharing effect is incorporated into the bias-dependent RDS This bias dependence is closely related to the drain/source doping profile and the channel dopant concentration. The proposed leffand RDSextraction method has been verified by an analytical I-V model which shows excellent agreements with the measured I-V characteristics.