Abstract: A method for fabricating a variable threshold IGFET free of parasitic effects and the "floating gate" effect.The method comprises forming a semi-conductive substrate of a first conductivity type material, forming a pair of laterally spaced diffusion regions of opposite conductivity type to the substrate material adjacent one surface of the substrate and forming a variable thickness oxide layer having a portion of minimum thickness with a predetermined width at least partially overlying the interstitial portion of the substrate, a portion of intermediate thickness substantially greater than the minimum thickness and partially overlying the interstitial substrate portion and at least one of the pair of spaced diffusion regions, and a remaining portion of maximum thickness substantially greater than the intermediate thickness.