| 摘要 |
A method for fabricating a semiconductor device is provided to improve a refresh characteristic by forming an oxide layer only on an interface of a recess gate structure, a silicon epitaxial layer under a bitline contact region and a semiconductor substrate. A SiGe epitaxial layer and a first silicon epitaxial layer are formed on a substrate(110). A first mask pattern is formed which exposes a storage node contact region and a part of a gate formation region adjacent thereto. The silicon epitaxial layer and the SiGe epitaxial layer are etched to expose the substrate. A planarized second silicon epitaxial layer(123) is formed to bury the remaining silicon epitaxial layer and SiGe epitaxial layer. A predetermined thickness of the substrate in a device formation region is etched to form a trench. The SiGe epitaxial layer is eliminated. An isolation layer(135) is formed to define an active region, burying a space from which the SiGe epitaxial layer is removed and the trench. A second overlap mask pattern is formed which exposes an overlapped portion of second and third masks. A predetermined thickness of the exposed mask layer and the second silicon epitaxial layer is etched to form a recess gate region. The second overlap mask pattern is removed to expose the active region. A gate insulation layer(140) is formed on the exposed active region. A gate electrode for burying the recess gate region is formed in a gate region to form a gate structure.
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