This paper presents an extensive mathematical study of a proposed nanogap-embedded dopant-segregated (DS) Schottky barrier (SB) cylindrical gate all-around (CGAA) metal-oxide-semiconductor field-effect transistor (MOSFET) of negatively/positively charged and neutral species observed by numerical simulation using an Atlas three-dimensional device simulator for electrical and label-free detection of bio/chemical (DNA, pH) and neutral species (protein) respectively as a nanosensor in the biomedical field at high sensitivity for direct electronic readout. This is the first time that the use of a nanogap-embedded DS-SB-CGAA MOSFET as a bio/chemical sensor has been reported. The threshold voltage (V th) shift and change in current are considered as sensing metrics to detect biological or chemical species when they are immobilized in the carvel-built region. The shift in on current (I on) of the nanogap-embedded DS-SB-CGAA MOSFET is also taken as a sensing metric, and better performance is observed compared to a conventional SB-CGAA MOSFET sensor. It is advantageous in terms of its low power/energy consumption as well as from the point of view of integration with the forthcoming silicon-based lab-on-chip systems due to the compatibility with the complementary metal-oxide semiconductor process.