The I-D-Y-G characteristics of short channel devices are analyzed to derive the E-eff dependent mobility and the device parameters including the series resistance, R. The exact gradual channel model is used to extract the surface potential and the vertical electric field, E-eff. Based on the experimental data that r(D) linearly depends on 1/(V-G -V-T), the formula for mobility-E-eff dependence should have two fitting parameters. Five possible formulas are advised, and they are found to fit equally well in the NMOS devices from five different technologies. It is verified that the mobility decreases linearly with E-eff by assuming that the maximum mobility, mu(0) obtained by extrapolating down to E-eff = 0, is close to the bulk mobility. Compared with a similar analysis as given above, the simple extraction method previously proposed by the author cannot predict the mobility at E-eff = 0, but predicts R and Delta L-G accurately, and is considered useful in quickly extracting the device parameters of scaled devices.