Dual thickness gate oxide fabrication method using plasma surface treatment

摘要

A method of forming on a common semiconductor body (substrate) silicon oxide layers of different thicknesses uses plasma treatment on selected portions of an original thermally grown silicon oxide layer. The plasma treated portions are completely etched away to expose a portion of the surface of the body while non-selected portions of the original silicon oxide layer are little effected by the etch. A thermally grown second layer of silicon oxide is formed with the result being that the silicon oxide layer formed in the exposed portions of the body is thinner than elsewhere. The use of dual thickness silicon oxide layers is useful with dynamic random access memories (DRAMs) as gate oxide layers of field transistors of memory cells of the DRAM typically require different electrical characteristics than transistors of support circuitry of the DRAM.