We present the extraction of MOSFET model parameters as functions of the channel length by means of a procedure based on the use of the measured source-to-drain resistance, instead of the conventional direct fitting to the drain current characteristics. Doing so, allows to separately extract the two parameters, source-and-drain series resistance and mobility degradation factor, that give rise to comparable effects on the current-gate voltage characteristics. The procedure involves a bidimensional fitting of the source-to-drain resistance as obtained from the below-saturation output characteristics measured at several above-threshold gate voltages. Its application is illustrated on experimental DRAM MOSFET test devices with channel lengths ranging from 0.23 to 2.0 m. It is shown that the new procedure is able to overcome the common difficulty typically encountered when trying to separate the effects of these two parameters using more conventional extraction methods.