In this chapter, favorable effect on Double gate MOSFET performance for subthreshold operation with the independent gate, asymmetric and underlap features in comparison to tied gate, symmetric, non-underlap features has been demonstrated. A novel analytical subthreshold potential model has been developed using conformal mapping. Using the developed potential model, other important subthreshold device performance parameters such as subthreshold current, subthreshold swing, threshold voltage, threshold voltage roll-off and DIBL effects are modeled. The developed models are validated with few published models, available experimental data and TCAD device simulations. Overall, the models demonstrate that gate underlap feature and asymmetry brought in device by proper tuning of back gate bias, back gate oxide thickness and gate work function materials adds more flexibility for tuning of DGMOSFET device threshold voltage values, minimizing subthreshold leakage currents and improved subthreshold swing values which are not found with tied gate, symmetric and non-underlap DGMOSFET models. © 2012 Nova Science Publishers, Inc. All rights reserved.