Alignment tolerance for a vertical gate transistor device can be relaxed because of a spacer formed adjacent the trench. The gate electrode is formed of two materials that have etch selectivity between them, such that the outer material can be etched a predetermined depth into the recess without etching...http://www.google.de/patents/US6677205?utm_source=gb-gplus-sharePatent US6677205 - Integrated spacer for gate/source/drain isolation in a vertical array structure
