Quantitative Extraction of Electric Flux in the Buried-Oxide Layer and Investigation of Its Effects on MOSFET Characteristics

Silicon-on-insulator (SOI) MOSFETs have advantages over conventional bulk MOSFETs in terms of their electrical characteristics, but also have inherent disadvantages due to the presence of their buried-oxide (BOX) layers. In this paper, focus was placed on drain electric flux passing via the BOX layer to the body region as an influence that induces disadvantages such as drain-induced barrier lowering in SOI MOSFETs. The electric flux in the BOX layer was visualized using stream functions, and was quantitatively evaluated for the first time ever. The results showed the dependence of electric flux on relative permittivity and the BOX layer thickness. These outcomes confirmed that the subthreshold slope (SS) in short-channel SOI MOSFETs is affected strongly by electric flux detouring via the BOX layer, and the compact model of the enhancement of SSs due to the flux is proposed.