A time-resolved analysis of the capacitance-voltage (C-V) technique and an inverse modeling approach have been developed to determine the energy distribution and the capture cross section of interface traps in the silicon band gap from multifrequency C-V measurements. In this work, our method is performed on n-type metal-oxide-semiconductor capacitors with HfSixOy/HfO2 gate dielectric stack and polysilicon gate. From the frequency dispersion of C-V data, we evidence a peak of acceptor states in the upper half of the band gap at 0.81 eV above the valence band and characterized by a capture cross section of 1.5x10(-17) cm(2). This value is approximately ten times lower than typical capture cross sections relative to the dangling bonds (P-b centers) at the Si/SiO2 interface, which is in good agreement with a Coulombic center model predicting a capture cross section inversely proportional to the square of the dielectric permittivity. (C) 2002 American Institute of Physics.