Abstract: A method for adjusting the leakage current of insulated gate field effect transistors comprised of silicon mesas epitaxially formed on a sapphire substrate, wherein the leakage current of a P channel transistor is increased by preoxidizing the silicon prior to standard processing and/or wherein the leakage current is decreased by annealing the silicon in a reducing atmosphere in addition to standard processing steps. The leakage current of an N channel transistor is reduced by preoxidizing the silicon of the transistor prior to forming the transistor and/or is increased by annealing in a reducing atmosphere in addition to the steps necessary for forming the transistor.

Abstract: A process for forming a blind hole having an isosceles trapezoidal cross-section in a sapphire substrate using a sulfur hexafluoride gas etchant and an etch mask of silicon nitride on top of silicon dioxide. A composite of sapphire, silicon dioxide and silicon nitride wherein silicon dioxide is located in between the sapphire and the silicon nitride; and the silicon nitride and silicon dioxide are congruently apertured.