Manufacturing of a low-noise mos device

摘要

At the surface of a substrate a gate oxide layer is produced and is given a dual thickness. A first oxide layer is produced over the surface of a substrate by thermal oxidation and is covered by a mask layer defining suitably located openings. A material accelerating or retarding the oxidation of the substrate is ion implanted through the first oxide layer in the openings, after which the mask is removed and the thermal oxidation is continued over the now exposed total surface of the first oxide layer. The material used for ion implanting can be an oxidation rate promoting material such as chloride and bromine. The manufacturing method is simple and adds little to presently used process flows for fabricating MOS devices. The dual thickness of the gate oxide gives the manufactured MOS device a low level of total noise generated when using the device for instance in RF-circuits.