An underlapped hetero-structure electrolyte Bio-TFET for potential of hydrogen (pH) sensing has been presented in this article. Intersection charge density ( [Formula: see text]) near the substrate-oxide junction can be employed to represent pH value within the simulation. A feasible fabrication scheme for the proposed model is specified here. A detailed simulation is performed with an ATLAS device simulator to examine the efficiency of the projected sensor. The impact of pH alterations on device features akin to the drain current ( [Formula: see text]), threshold potential ( [Formula: see text]), sensitivity regarding voltage ( [Formula: see text]), and current ( [Formula: see text]) is examined. The effect of phosphate-buffered saline (PBS) concentrations on the pH buffer are also scrutinized. Moreover, the impact of the reference voltage and current ( [Formula: see text] and [Formula: see text]), and channel doping concentration ( [Formula: see text]) over [Formula: see text] and [Formula: see text] is analyzed methodically. Here, [Formula: see text] attains ≈100 mV/pH, which is superior to the Nernstian limit (59 mV/pH) and [Formula: see text] enhances nearly ten times per pH variation. Benchmarking is included to provide a quantitative assessment of the proposed model with the published literature. The impact of temperature on pH buffer, [Formula: see text], temporal drift parameters and sensitivities have been emphasized. Finally, the temperature-immunity aspect of the proposed Bio-HTFET based pH sensor is highlighted by comparing sensitivity parameter among state-of-the-art literature. Hence, the recommended pH sensor can be utilized as an outstanding substitute for the succeeding generation of biosensor applications.