It has been found from ac conductance measurement that two kinds of interface states are generated in the upper half of the gap when (100)n‐Si metal/oxide/semiconductor capacitors are subjected to Fowler‐Nordheim tunneling electron injection. The generation efficiency of these interface states varies in a quite similar fashion with the oxide voltage, although the magnitude is somewhat different from each other. The electron capture cross section for both interface states shows a curious behavior that its value decreases with increasing interface‐state density when exceeding about 1.5×1011cm−2eV−1. This behavior is explained in terms of the occurrence of additional tunneling to defect states in the oxide. ©1996 American Institute of Physics.