In this work, the performance of a Double-Gated Silicon on Insulator (DG-SOI) Dielectrically Modulated Tunnel Field Effect Transistor (DMTFET) architecture is systematically investigated for label-free bio-sensing applications with the help of extensive device-level simulations. In this context, the effects of bulk oxide (BOX) substrate and back-gate biasing are emphasized and analyzed from the cavity and channel electrostatics and Band to Band Tunneling (BTBT) component of DMTFET. It is found that the electrostatic coupling between BOX substrate and channel significantly degrades the sensing performance of DG-SOI DMTFETs, whereas an applied negative back-gate bias enhances the performance of such transducer. In this line, a dual metal (DM) gate architecture is introduced that can effectively enhance the influence of applied back-gate bias and thereby leads to sensitivity improvement from 10% to 110% in DM DG-SOI DMTFET depending on bio-molecule sample specifications. Furthermore, it is observed that for suitable applied back-gate bias, the interface trap-state induced variations in sensitivity of DG-SOI DMTFETs can be reduced by even an order of magnitude. Finally, a comparative sensing performance study of proposed DMTFET with their reported counterparts establishes the advantage of such biosensors for bio-molecules with smaller dielectric constant. A similar study also shows the superiority of the proposed DMTFET over its MOSFET counterpart for wide bio-molecular sample specifications.