To readily and in approximation compute interface state density on the interface of an SOI(silicon-on-insulator) thin-film and an insulating layer, in an SOI substrate, even when impurity concentration in the SOI thin-film cannot be obtained accurately. SOI薄膜中の不純物濃度が正確に求められない場合にも、SOI基板のSOI薄膜と絶縁層との界面における界面準位密度を簡便にかつ近似的に算出する。 - 特許庁