Some embodiments include a method of forming a capacitor. An opening is formed through a silicon-containing mass to a base, and sidewalls of the opening are lined with protective material. A first capacitor electrode is formed within the opening and has sidewalls along the protective material. At least some of the silicon-containing mass is removed with an etch. The protective material protects the first capacitor electrode from being removed by the etch. A second capacitor electrode is formed along the sidewalls of the first capacitor electrode, and is spaced from the first capacitor electrode by capacitor dielectric. Some embodiments include multi-material structures having one or more of aluminum nitride, molybdenum nitride, niobium nitride, niobium oxide, silicon dioxide, tantalum nitride and tantalum oxide. Some embodiments include semiconductor constructions.