In this article, for the first time, the performance of a double-hetero-gated-dielectric-modulated tunnel FET (DHGDM-TFET) biosensor device, having channel length (Lch) of 50 nm, is thoroughly investigated in terms of threshold voltage- ( VTH-), subthreshold swing- (SS-), ON-current- (ION-), and OFF-current- ( IOFF-) sensitivity parameters, in order to find its suitability in successful detection and identification of different biomolecules. The investigation is further extended to the optimization of the proposed sensor device, against cavity length (LCavity) and misalignment effect between the cavity and high-k dielectric, underneath the cavity of the sensor device. It is found that our proposed biosensor device works at its optimum with LCavity=10 nm, while the cavity is perfectly aligned with the underneath high-k of the device. Furthermore, a comparison of our proposed device is performed against its equivalent high- k only and SiO2 only TFET-based biosensors. For each aforementioned sensitivity parameter, it is found that our proposed DHGDM-TFET biosensor device outperforms the rest two devices, proving the superiority in sensing action. © 1963-2012 IEEE.