Abstract: A method for manufacturing a gate dielectric layer is provided. A substrate divided into at least a high voltage circuit region and a low voltage circuit region is provided. A first dielectric layer serving as gate dielectric layer in the high voltage circuit region is formed on the substrate. A mask layer is formed over the first dielectric layer. The mask layer, the first dielectric layer and the substrate are patterned to form trenches in the substrate. An isolation layer is formed to fill the trenches. The mask layer and part of the isolation layer are removed to expose the surface of the first dielectric layer. The first dielectric layer of the low voltage circuit region is removed to expose the surface of the substrate. A second dielectric layer having a thickness smaller than the first dielectric layer is formed on the substrate in the low voltage circuit region.

Abstract: A method for manufacturing a gate dielectric layer is provided. A substrate divided into at least a high voltage circuit region and a low voltage circuit region is provided. A first dielectric layer serving as gate dielectric layer in the high voltage circuit region is formed on the substrate. A mask layer is formed over the first dielectric layer. The mask layer, the first dielectric layer and the substrate are patterned to form trenches in the substrate. An isolation layer is formed to fill the trenches. The mask layer and part of the isolation layer are removed to expose the surface of the first dielectric layer. The first dielectric layer of the low voltage circuit region is removed to expose the surface of the substrate. A second dielectric layer having a thickness smaller than the first dielectric layer is formed on the substrate in the low voltage circuit region.