General treatment of charge transfer at electrochemical interfaces is based on charge carrier concentration and activation enthalpy of the transfer step. For the description of electron transfer at semiconductor electrodes, energy-level diagrams have proved useful, giving a detailed picture of the nature of the interface. In the case of semiconducting ionic electrodes, however, energy-level diagrams are currently not being utilized. The reason is insufficient knowledge regarding ion energy levels and nature of double layer. This contribution briefly reviews the fundamentals of charge transfer at semiconducting electrodes and discusses the establishment of energy-level diagrams for semiconducting ionic electrodes.