Aspects describe gas sensitive field effect transistor (FET) structures, a gas sensitive FET array including the disclosed gas sensitive FET structures, and methods of manufacturing and using the same. In one example, a gas sensitive FET structure can include a body comprising a substrate layer, an intermediate layer over the substrate layer, and a passivation layer over the intermediate layer. Primary terminals disposed within the body can include at least one source terminal, at least one drain terminal and at least one gate terminal. A floating gate disposed within the body can comprise metal at a top surface of the intermediate layer. The passivation layer can be etched over the floating gate, and the floating gate can be electrically coupled to the gate terminal of the primary terminals. A sensing material layer can be positioned over the floating gate. A reset element can be included for resetting the floating gate.