Semiconductor device structures

Methods of forming features are disclosed. One method comprises forming a resist over a pool of acidic or basic material on a substrate structure, selectively exposing the resist to an energy source to form exposed resist portions and non-exposed resist portions, and diffusing acid or base of the acidic or basic material from the pool into proximal portions of the resist. Another method comprises forming a plurality of recesses in a substrate structure. The plurality of recesses are filled with a pool material comprising acid or base. A resist is formed over the pool material and the substrate structure and acid or base is diffused into adjacent portions of the resist. The resist is patterned to form openings in the resist. The openings comprise wider portions distal to the substrate structure and narrower portions proximal to the substrate structure. Additional methods and semiconductor device structures including the features are disclosed.