Semiconductor components are often fabricated that include a nickel silicide layer, e.g., as part of a gate electrode in a transistor component, which may be formed by forming a layer of nickel on a silicon-containing area of the semiconductor substrate, followed by thermally annealing the semiconductor substrate to produce a nickel silicide. However, nickel may tend to diffuse into silicon during the thermal anneal, and may form crystals that undesirably increase the sheet resistance in the transistor. Carbon may be placed with the nickel to serve as a diffusion suppressant and/or to prevent nickel crystal formation during thermal annealing. Methods are disclosed for utilizing this technique, as well as semiconductor components formed in accordance with this technique.