A unified MOSFET model has been developed, which is valid for submicron ranges, and takes into account the following effects of deep submicron MOSFETs: short and narrow channel effects, mobility reduction due to vertical field, carrier velocity saturation, and channel length modulation. The model uses a single I-V expression to describe the current, transconductance, and output conductance characteristics from weak to strong inversion region. Furthermore, the proposed model is continues for all regions of operation to ensure the capability of using the model for analog and low level voltages applications. The small number of model parameters was one of the target points during the development of this model. The validity of the model has been checked by making comparison with experimental data for n-channel and p-channel MOSFET transistors having different channel lengths and widths. Moreover, The proposed model shows better accuracy in comparison with other well-known models like SPICE LEVEL 1, 2, 3, and 4. Although, the model is simple in nature and has small number of model parameters, it shows good accuracy and smooth transition for the current, transoconductance, and output conductance in comparison with the other models which they display a discontinuity for these parameters at the transition regions.