Abstract: A method of manufacturing and inspecting SOI such that during STI formation, by depositing a light absorbing layer in the STI such as hydrosilicon oxynitride, the silicon inclusions in the buried insulator layer of the SOI are undetectable by an optical inspection. The reduction in background effects allows for improved optical inspection of SOI wafers without having to discriminate against defects created by SOI formation. A method of manufacturing and inspecting semiconductor devices is disclosed wherein deposition of a light absorbing layer, such as hydrosilicon oxynitride, prevents defects occurring prior to deposition from being optically inspectable and those defects created during the most recent processing can be easily distinguished. Also disclosed are an optically inspectable semiconductor device and an optically inspectable semiconductor device having an STI.