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The atomic structure of amorphous and crystalline hafnium oxide ͑HfO 2 ͒ films was examined using x-ray diffractometry and Hf edge x-ray absorption spectroscopy. According to the x-ray photoelectron spectroscopy and band data calculated by the density functional method, we found that the valence band of HfO 2 consists of three subbands separated by ionic gaps. The upper subband is formed by O 2p, Hf 4f, and Hf 5d states; the intermediate subband is formed by O 2s and Hf 4f states, whereas the lower narrow subband is mainly formed by Hf 5p states. The energy gap of amorphous HfO 2 is 5.7 eV as determined by electron energy loss spectroscopy. The band calculation results indicate the existence of light ͑0.3m 0 ͒ and heavy ͑8.3m 0 ͒ holes in the HfO 2 film and the effective mass of electron lies in the interval of 0.7m 0-2.0m 0 .

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