This paper presents a review of the main properties of the two types of buried oxides that currently dominate the Silicon-On-Insulator (SOI) technologies: SIMOX (Separation by IMplantation of OXygen) and BESOI (Bond and Etch-Back SOI) materials. After examining the main advantages of SOI structure for radiation-hardened electronics, we present different advanced technological processes of such buried oxides and review their physical characteristics as well as their charge trapping properties under ionizing radiations.