| 摘要 |
For fabricating a metal oxide structure on a semiconductor substrate, an active device area surrounded by at least one STI (shallow trench isolation) structure is formed in the semiconductor substrate. A layer of metal is deposited on the semiconductor substrate, and the layer of metal contacts the active device area of the semiconductor substrate. A layer of oxygen blocking material is deposited on the layer of metal. An opening is etched through the layer of oxygen blocking material to expose an area of the layer of metal on top of the active device area. A thermal oxidation process is performed to form a metal oxide structure from reaction of oxygen with the area of the layer of metal that is exposed. A thickness of the metal oxide structure is determined by a thickness of the layer of metal, and the layer of oxygen blocking material prevents contact of oxygen with the layer of metal such that the metal oxide structure is formed localized at the area where the layer of metal is exposed. In this manner, the metal oxide structure is formed by localized thermal oxidation of the layer of metal such that a deposition or sputtering process or an etching process is not necessary for formation of the metal oxide structure. In addition, the thickness of the metal oxide structure is determined by controlling the thickness of the layer of metal used for forming the metal oxide structure. Furthermore, these steps may be repeated for another layer of metal having a different thickness for forming a plurality of metal oxide structures having different thicknesses to provide gate dielectrics of MOSFETs (metal oxide semiconductor field effect transistors) having different threshold voltages on the same semiconductor substrate.
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