In a hybrid microwave integrated circuit in which an FET and an LC resonance circuit are integrated, the LC resonance circuit includes an inductor and a capacitor disposed on a substrate having a smooth surface which ensures that the dimensional precision of the inductor will be in a range of.+-.several microns when it is formed on the substrate. Then, the substrate, on which the LC resonance circuit is formed, is mounted on or buried in a high frequency signal transmitting substrate. Therefore, variation in resonant frequency of the LC resonance circuit are reduced, whereby deteriorations in characteristics, such as efficiency, output power and the like, are reduced. In addition, since the LC resonance circuit is reduced in the size and cost of the whole circuit are reduced.