Importance

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Abstract

A process for fabricating a semiconductor device. In an exemplary embodiment, the process includes the following steps. The process initially defines a first registration mark associated with a first mask level of the semiconductor device and a second registration mark associated with a second mask level of the semiconductor device. The process then defines a third registration mark associated with a third mask level of the semiconductor device based on the first and second registration marks. Finally, the process aligns the third mask level along a first axis with respect to the first registration mark, and aligns the third mask level along a second axis with respect to the second registration mark. According to various aspects of the invention, the semiconductor fabrication process is used to fabricate DRAM trench cells, or any other type of semiconductor device whose fabrication requires tight overlay alignment between the various levels of the device.

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First Claim