In this paper, for the first time, a unique pTFET-based biosensor device having channel epilayer has been introduced and its performance in the sensing domain has been studied in terms of five different sensitivity parameters. A rigorous analysis of the effect of the existent corner point (corner-effect) in the proposed device architecture on the sensitivity metrics has been performed for five different channel epilayer thicknesses, covering five different types of protein-molecules, viz., Apomyoglobin, Myoglobin, Protein-G, Ferricytochrome-C, and Ferrocytochrome-C. This is followed by determining detectability and optimum length-window of nanogap cavity of the proposed sensor device for the successful detection. Interestingly, it has been found that the undesired corner-effect, generally known for its unfavorable impact on the electrical behaviors of the MOS-based structures, actually comes to the aid by enhancing the detectability of the proposed device compared to its equivalent conventional SOI pTFET sensor device by almost 67% (for Protein-G, Ferricytochrome-C, and Ferrocytochrome-C) and 50% (for Apomyoglobin and Myoglobin) yet maintaining significantly good values for the sensitivity metrics throughout. Furthermore, smaller epilayer thicknesses ensure smaller optimum length-window of the nanogap cavity, resulting in more scaled-down device, compared to larger epilayer thickness values. A position-dependent variability study for the detectability also follows, and it has been found that for small epilayer thicknesses this dependency becomes large leading to less stable device, although, at the same time producing higher sensitivity metrics compared to the devices having large epilayer thicknesses. This makes the choice of channel epilayer thickness as application-specific. © 2002-2012 IEEE.