We have studied the chemical bonding features and electronic states of ultrathin Hf-La oxide using high-resolution x-ray photoelectron spectroscopy (XPS). 6 nm-thick Hf-La oxides with different La/(Hf+La) content were prepared on wet-chemical cleaned p-type Si(100) and Pt layer by thermal decomposition of Hf(DPM: dipivaloymcthanato)₄ and La(DPM)₃ in O₂ ambient at 450℃. From XPS core-line analysis, diffusion and incorporation of Si atoms from the Si substrate into the Hf-La oxide film by 800℃ annealing in O₂ ambience were pronounced with increased La content over 35%. The energy band profile of the Hf-La oxide/Si system as a function of La content has been determined by a combination of oxide bandgap (Eg) values and valence band (VB) line-ups. The conduction band (CB) offset has been also estimated using the Eg of the Si substrate, measured Eg, and VB offset. The impact of Si incorporation into Hf-La oxide on CB and VB offsets between the Hf-La(:Si) oxide and Si substrate also discussed in comparison to the energy band diagram of the Hf-La oxide/Pt structure.