In this work, we examined the impact of gate work-function and back-gate bias to enhance sensing metrics of a Dielectric Modulated (DM) p-type Tunnel Field Effect Transistor (p-TFET) based biosensor. The sensing metrics, namely Sensitivity (S) and Selectivity (ΔS) are considerably improved by using a lower value of gate work-function and positive back gate voltages. It is shown that by appropriate selection of gate work-function and back gate bias, Band-to-Band Tunneling (BTBT) of carriers is reduced and a significant change in electrical characteristics is observed in a device with an empty cavity. Therefore, the relative change in the drain current due to the presence of biomolecules in the nanogap cavity is maximized. Results indicate a Sensitivity of ∼109 for 3-aminopropyltriethoxysilane (APTES) biomolecule, and Selectivity of ∼102 for APTES concerning Biotin biomolecule in an optimally designed p-TFET biosensor. The impact of location, as well as the charge of biomolecules, are also analyzed in this work. Results showcase the additional degree of freedom through device optimization which facilitates the tunability of sensing metrics for improved biosensor performance. © 2020 IOP Publishing Ltd.