A semiconductor device includes a silicon substrate and a detection element and p-type and n-type MOS transistors, which are arranged on the silicon substrate, wherein the detection element includes a semiconductor layer, electrodes, and a Schottkey barrier disposed therebetween, the semiconductor layer is arranged just above a layer having the same composition and height as those of an impurity diffusion layer in the source or drain of the p-type or n-type MOS transistor, a region, in the silicon substrate, having the same composition and height as those of a channel region, in the silicon substrate, just below a gate oxide film of the p-type MOS transistor or the n-type MOS transistor, or a region, in the silicon substrate, having the same composition and height as those of a region just below a field oxide film disposed between the p-type and the n-type MOS transistor.