The present invention provides a method of forming a semiconductor device. A layer of photoresist is applied to a semiconductor wafer. A first mask is used to protect a first portion of the photoresist while a second portion of the photoresist is exposed. A second mask is used to expose a third portion...http://www.google.es/patents/US5338397?utm_source=gb-gplus-sharePatente US5338397 - Method of forming a semiconductor device
