The behaviour of SiO/sub 2//Si structures irradiated by high energy (> 0.5 GeV) Xe and Ni ions has been investigated. Structural analysis of the as-irradiated SiO/sub 2/ films, performed with infrared spectroscopy, indicates atomic displacements, broken and strained Si-O bonds induced by irradiation. Electrical measurements of irradiated SiO/sub 2//Si structures show an increase of the interface state density Dit and of the oxide trapped charge density. Not with the fluence. Electrically active defects were detected in Si substrate and are associated with vacancy complexes. >