In United States Patent 7,625,766, Micron Technology, Inc. (Boise, ID) scientist Gurtej S. Sandhu reveals a method of using carbon nanotubes to fabricate integrated circuitry. First a step wall is formed over a substrate. Catalytic material of different composition than the step wall is provided proximate thereto. A carbon nanotube is grown from the catalytic material along the step wall generally parallel to the substrate. A method of fabricating integrated circuitry includes forming a step wall over a semiconductor substrate. Catalytic material is provided proximate the step wall. An elevationally outer surface of the catalytic material is masked with a masking material. The catalytic material and the masking material are patterned to form an exposed end sidewall of the catalytic material proximate the step wall, with remaining of the elevationally outer surface of the catalytic material being masked. A carbon nanotube is grown from the exposed end sidewall of the catalytic material along the step wall generally parallel to the semiconductor
