A thin film transistor utilizing an insulated gate structure is described wherein the semiconducting layer is formed of defectnickel oxide having the general formula Ni(1 x)O, wherein x is within the range of 10 7 to 10 2. In a preferred embodiment, the insulating layer overlying the defect-nickel oxide semiconducting layer is formed of stoichiometric nickel oxide thereby reducing the number of steps required in fabrication. The thin film transistor is fabricated within a single system by utilizing reactive sputtering for the formation of the semiconducting and insulating layers. The sputtering takes place in a pure oxygen atmosphere in the absence of inert gases with the result that the characteristics of the deposited nickel oxide films can be varied by controlling the deposition rate during sputtering.