gate oxides having different thicknesses are grown on a semiconductor layer by the process which comprises forming a semiconductor layer on a substrate , growing an oxide layer on the semiconductor layer , exposing a selected area of the oxide layer , amorphizing the semiconductor layer underlying the exposed oxide layer , removing the oxide layer to expose the semiconductor layer having both amorphized and non - amorphized regions and growing gate oxide on the amorphized and non - amorphized regions of the semiconductor layer . gate oxide grown on the amorphized regions will be thicker than gate oxide grown on the non - amorphized regions . the process of the invention obviates the need for special integrated circuit manufacturing design modifications and can be utilized to fabricate a wide variety of devices , in particular , mos - type devices .