In a semiconductor device that includes a first level conductor layer, a second level conductor layer, and a third level conductor layer, the second level conductor layer being positioned at a level between the first and third level conductor layers, a contact hole for electrically connecting the first...http://www.google.ca/patents/US5422315?utm_source=gb-gplus-sharePatent US5422315 - Method for forming self-aligned contact hole and semiconductor device having self-aligned contact hole
