| 摘要 |
A process for fabricating a semiconductor device having deep trench structures includes forming a first portion of the trench in a semiconductor substrate and a second portion of the trench in a selectively-formed upper layer. After etching the substrate to form the first portion of the trench, a protective layer is deposited over the inner surface of the trench in the semiconductor substrate and the upper layer is selectively formed on a principal surface of the semiconductor substrate. During formation of the upper layer, a wall surface is formed in the upper layer that is continuous with the wall surface of the trench in the semiconductor substrate. By forming a second portion of the trench in the selectively-formed upper layer, a deep trench is produced having a high aspect ratio and well defined geometric characteristics.
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