The physics model and electrical characteristics of the silicon and germanium based tunneling double gate field-effect transistor are discussed for low power logic applications using two dimensional device simulation. Ge has a property of high band-to-band tunneling rate as compared to Si, the Ge-DGTFET suffers from uncontrolled off-state leakage current I off rather than its higher on-state current I on . It is also shown increasing I on with a steeper subthreshold swing SS, source doping concentration is increased to reduce the bandgap and this will narrow the tunneling width. Device design and physics model presenting the impact of Electric field, surface potential model, gate work function,Source Doping and gate oxide variation on the performance of Ge-DGTFET and Si-DGTFET are discussed. The simulations have been carried out on Sentauras TCAD tool.