Multiple etch method for fabricating spacer layers

Within a method for forming a spacer layer from a second layer formed of a second material laminated upon a first layer formed of a first material, in turn formed over a topographic feature, there is employed a three step etch method. The three step etch method employs: (1) a first etch method having a first enhanced etch selectivity for the second material with respect to the first material; (2) a second etch method having a second substantially neutral etch selectivity for the second material with respect to the first material; and (3) a third etch method having a third enhanced etch selectivity for the first material with respect to the second material. In accord with the three step etch method, the spacer layer is fabricated with enhanced dimensional control.