Method of making stabilized silicon-on-insulator field-effect

Abstract

A MOS/SOI field-effect transistor is made by applying a layer of a photoresist over the surface of a single-crystalline silicon layer which is on a substrate of an insulating material, such as sapphire. The surface of the silicon layer is along a (100) crystallographic plane. The photoresist layer is defined to provide an area of the photoresist layer over the area of the silicon layer where the transistor is to be formed with the edges of the photoresist area being along the edges of (100) crystallographic planes which are perpendicular to the surface of the silicon layer. The portion of the silicon layer around the photoresist layer is etched with an anisotropic plasma etch which etches the silicon layer along the (100) crystallographic planes which are perpendicular to the surface of the silicon layer to form an island of the silicon. The etching is achieved by a two step process in which the first step etches part way through the silicon layer and the second step etches completely through with an overetch. This forms the silicon island with sides which extend along (100) crystallographic planes substantially perpendicular to the top surface and which are smooth, undamaged and have rounded edges with the top surface. After removing the photoresist, a MOS field-effect transistor is formed on the island.