In the nano regime it has become increasingly important to consider the impact of non-rectangular gate (NRG) shape caused due to sub-wavelength lithography. NRG dramatically increases the leakage current and requires geometry dependent transistor models for post-litho circuit simulation. In this paper, we propose a coherent modeling approach for non-rectangular gates based on equivalent gate length (L e). A gate-voltage dependent model of L e is developed which is scalable with design conditions, continuous across weak and strong inversion regions, accurate for both leakage and saturation current, and compatible with standard circuit analysis tools. We systematically verify this approach with 65nm TCAD simulations. A generic CAD algorithm is further proposed to predict the value of L e under various non-rectangular geometries. The interaction with the narrow-width effect is efficiently convolved in this method. Depending on the gate geometry, the leakage current can vary more than 15X at 65nm technology node. Our analytical method well captures this effect. Finally, we extrapolate the impact of NRG effect on future technology generations. The proposed model can be easily extracted from TCAD tools or direct silicon data. It bridges the gap between lithography, simulation, and circuit analysis for measuring transistor performance under increasingly severe NRG effect.