A local oscillation FET has a source connecting pad, a drain connecting pad and a gate connecting pad. The source connecting pad occupies one comer of a substrate, and the drain and gate connecting pads are placed at the neighboring comers so that the three connecting pads form an L shape on the substrate. As a modification to this configuration, another source connecting pad is placed at the remaining comer of the substrate so that the drain and gate connecting pads are shielded from each other by the two source connecting pads. These device configurations contribute to size reduction of the local oscillation FET.