A semiconductor device includes a switching element, for example, a Schottky barrier diode, which controls transmission/cutoff of a signal transmitted between two portions of a transmission line. An anode electrode of the switching element is interposed between the two portions of the transmission line and the longitudinal direction of the anode electrode is aligned with the longitudinal direction of the transmission line. A cathode electrode of the switching element is disposed on at least one of the widthwise sides of the anode electrode, and is connected to ground.