A method for fabricating semiconductor device structures includes forming a non-conformal mask over a surface of a substrate. Non-conformal mask material with a planar or substantially planar upper surface is formed on the surface of the substrate. The planarity or substantial planarity of the non-conformal material eliminates or substantially eliminates distortion in a “mask” formed thereover and, thus, eliminates or substantially eliminates distortion in any mask that is subsequently formed using the pattern of the mask. In some embodiments, mask material of the non-conformal mask does not extend into recesses in the upper surface of the substrate; instead it “bridges” the recesses. Semiconductor device structures that include non-conformal masks and semiconductor device structures that have been fabricated with non-conformal masks are also disclosed.