A compact channel-current model is proposed for the linear, saturation and sub-threshold regions of MOSFETs with eight parameters at the maximum. To derive new formulas both physically reasonable and analytically simple, the core part of the known theories and formulas including BSIM is carefully examined, and the comparison with the exact gradual model is made. A simple formula for the linear region is obtained considering the velocity saturation effect, the bias dependent mobility and the series resistance in the source and drain junctions. It is theoretically predicted and experimentally confirmed that the two new parameters in the denominator strongly depend on the channel length. Simple expressions are additionally advised for the saturation and the sub-threshold regions. By applying the model to a set of devices covering a wide range of channel length, the parameters are extracted, and good agreement between theory and measurement is demonstrated. (c) 2006 Elsevier Ltd. All rights reserved.