PURPOSE: To make the size of the device small by using a conductive layer bent in an L-shape so as to form a pre-matching circuit.

CONSTITUTION: Input and output side pre-matching circuits 14, 17 are formed by using an L-shaped microstrip line. Furthermore, the circuits 14, 17 are arranged to a corner of a board 2 and a chip 1 is arranged so that a direction of a line segment tying a gate lead 6 and a drain lead 9 and a lengthwise direction of a FET chip 1 are made parallel. As a result, the area of the board 2 is decreased while keeping the characteristic of the circuits 14, 17 and the device is made small. Furthermore, a tri-plate line of a structure of three conductor layers laminated via a dielectric layer may be used in place of the microstrip line.