Multiple etch method for fabricating spacer layers

A method for fabricating a spacer layer comprising:

• providing a semiconductor substrate having formed thereover a topographic feature;
• forming over the semiconductor substrate including the topographic feature a first layer of a first material having formed thereupon a second layer of a second material;
• etching, while employing a first etch method having a first enhanced etch selectivity for the second material with respect to the first material, the second layer to form therefrom a second spacer layer formed upon the first layer;
• etching, while employing a second etch method having a second substantially neutral etch selectivity for the second material with respect to the first material, the second spacer layer and first layer to form therefrom an etched second spacer layer formed upon a partially etched first layer;
• and
• etching, while employing a third etch method having a third enhanced etch selectivity for the first material with respect to the second material, the partially etched first layer to form a first spacer layer having formed thereupon the etched second spacer layer.

A method for fabricating a spacer layer comprising:

• providing a substrate having formed thereover a topographic feature;
• forming over the substrate including the topographic feature a first layer of a first material having formed thereupon a second layer of a second material;
• etching, employing a first etch method with a loss selectivity for the second material and the first material, the second spacer layer formed on a partially etched first layer;
• and
• etching, while employing a second etch method having an enhanced etch selectivity for the first material with respect to the second material, the partially etched first layers forming a first spacer on top of the second spacer layer.