Field-effect transistors, and apparatus including such field-effect transistors, including a gate dielectric overlying a semiconductor and a control gate overlying the gate dielectric. The control gate might include an instance of a first polycrystalline silicon-containing material containing polycrystalline silicon, and an instance of a second polycrystalline silicon-containing material containing polycrystalline silicon-germanium or polycrystalline silicon-germanium-carbon.