Abstract: A microwave semiconductor device of this invention is made by arranging a plurality of active regions of Schottky barrier FET on a single semiconductor substrate in a common gate width direction, and gate electrodes are linearly connected to each other. Side-gate electrodes each formed by an ohmic metal are arranged on the semiconductor substrate between adjacent active regions. In this portion, a gate wiring layer is arranged so as to cross over each side-gate electrode. With this arrangement, a sufficient side gate effect on the entire FET having gate electrodes connected to have a large length, can be obtained, and a threshold voltage can be controlled after manufacturing.