In this work, the hafnium oxynitride (HfON) nanorod films on p-type silicon (Si) wafer substrate have been fabricated by reactive magnetron sputtering with glancing angle deposition (GLAD) technique, subsequently with a rapid thermal oxidation process at 500–900 °C under low-vacuum state. The crystallinity and morphology were investigated by glazing-incident X-ray diffraction (GIXRD) and field-emission scanning electron microscopy (FE-SEM), respectively. As-deposited films were amorphous nanorod films. The surface-sensitive X-ray photoelectron spectroscopy (XPS) analytical technique revealed that nitrogen atoms are increasingly replaced with oxygen atoms at the surface. The distribution of nitrogen atoms investigated by X-ray absorption spectroscopy (XAS) revealed the substitution of nitrogen with oxygen at the film surface and molecular nitrogen trapped in the film as the annealing temperature was increased.