[en] This paper is focused on the properties of the SIMOX structure that are essential for the proper operation of integrated circuits. These properties are determined by direct inspection of the wafer or inferred from the characterization of test MOS devices. The next section presents the status of the SIMOX technology in terms of quality of the Si film, buried oxide and Si-SiO₂ interfaces. Interface coupling and floating body effects are typical phenomena in SOI transistors and are briefly discussed. Emphasis is put, in the last section, on reliability aspects which may be governed by the resistance of the buried oxide to hot carrier injection and radiation effects