We have investigated the relationship between band alignment and chemical states in HfSiON/SiON stacked films on Si substrates by photoemission spectroscopy and x-ray absorption spectroscopy. Valence-band maxima mainly derived from N 2p states in HfSiON films are closely related to N-Hf bonding configurations. The valence-band offset for a thick HfSiON film is smaller than that for a thin HfSiON film, due to the amount of N-Hf bonding states. Since N-Hf bonding states decrease upon annealing, thickness dependence of valence-band offset can be eliminated. On the other hand, the conduction-band offset does not depend on either the thickness or annealing.