To maintain the phase of harmonics uniform and to improve the efficiency by arranging harmonic matching circuits, consisting of a capacitor and an inductor between a semiconductor chip which connects a semiconductor cell to a gate pad and a drain pad and performs an amplification operation in a high frequency band and an output side internal matching circuit.

In this semiconductor device 200, a semiconductor chip 90 on which plural semiconductor cells connected to one gate pad 1 and one drain pad 2 are arranged on a semiconductor substrate performs an amplifying operation in a high frequency band. Harmonic matching circuits 22, consisting of a capacitor and an inductor which, are arranged between the chip 90, and an output side internal matching circuit 14 are housed together with the semiconductor substrate in a package. The circuit 22 processes harmonics in the neighborhood of the chip 90, maintains the phase of the harmonics uniformly and reduces the loss that is caused by the characteristic itself of the harmonics. Thus, phase difference that is caused by path difference is reduced, satisfactory harmonic load impedance is obtained, and efficiency is improved.