Patent ID: 6660593
Filing Date: 2003-12-09
Classification: H01L

Abstract:
A method for fabricating oxide layers of different thicknesses on a substrate, comprising:forming a field oxide layer on the substrate to define a first active region and a second active region therebetween; forming a first oxide layer over the first and the second active regions; implanting impurities into an upper portion of the first oxide layer, wherein the impurities depress the oxidation rate of the first oxide layer; removing the first oxide layer within the second active region; removing most of the upper portion of the remaining the first oxide layer within the first active region, thereby leaving a thin implanted oxide layer on a remaining portion of said first oxide layer; and oxidizing the substrate to form a second oxide layer over the second active region, wherein the second oxide layer has a thickness different from the thickness of the lower portion of the first oxide layer.