The method to determine the energy band alignments of high-k dielectrics to Si(100) is described, in which the energy band gap values and the valence band lineups are measured from the analyses of energy loss signals of core line and valence band spectra measured by X-ray photoelectron spectroscopy (XPS), respectively. Also, it is demonstrated how useful the measurement of the cut-of energy for photoemission is to evaluate the effective work function in metal/high-k dielectric. Total photoelectron yield spectroscopy (PYS) is highlighted as a powerful way to quantify energy distribution of electronic defect states in a dielectric or at the dielectric/Si interface in the energy region corresponding to the Si band gap.