We identify the physical origin of the excess capacitance at Schottky diodes without an interfacial layer, i.e., intimate Schottky contacts. Measured capacitance in excess of the space-charge capacitance is shown to be caused by the injection of minority carriers into the bulk semiconductor, rather than by the presence of interface states, as previously thought. Minority-carrier injection depends sensitively on the properties of the Ohmic back-contact.