The present paper proposes a dielectric modulation based Triple Gate Doping Less Tunnel Field Effect Transistor (TG-DLTFET) biosensor with a cavity introduced underneath the gate and source metal for symmetrical and asymmetrical device to recognize very small size biomolecules such as Amino Acids (AAs). The proposed n + pocket doped vertical device aims to achieve high sensitivity with lower short channel effects. The placement and width of the n + pocket layer within the source are reformed with the goal of acquiring the higher current switching ratio. The variation in the device’s electrical parameters (surface potential, drain current and sensitivity) corresponding to dielectric constant and charge density reflected the biorecognition process in the biosensor. Additionally, the impact of variations in device geometry (spacer length, cavity length, cavity thickness, and gate misalignment effects) on the drain current and drain current sensitivity of device have also been evaluated and reasoned, respectively. The results reflect that with proper choice of the geometric parameters, the device sensitivity can be attained up to 1010. Thus, the present findings reflected that TG-DLTFET has a better sensing capability as a biosensor, together with a low value of short channel effect and leakage current. The proposed n + pocket doped vertical device has a significant potential to detect varations in AAs and DNA.