To set an allowable range of characteristic impedance of a transmission circuit so as to obtain an excellent high-frequency characteristic, by providing a specified clearance between the surface of a coplanar transmission line on a semiconductor chip and that of an electrode on a substrate when flip-chip mounting a coplanar type MMIC chip to the substrate.

In an MM(monolithic microwave) IC chip, a bump is formed on the chip side, and the thickness of an Au bump 6-a or 6-b is adjusted in advance in consideration of compression in the heightwise direction of the Au bump by press-fitting, so that a clearance H between the surface of a coplanar transmission line and that of a substrate electrode is within 11 to 29 μm when the coplanar transmission line 8 made of Au layer for example is flip-chip mounted on an alumina substrate 7. Thus, the characteristic impedance of the coplanar transmission line can be set to a range of 50 Ω±2 Ω. The attenuation or reflection of a high-frequency signal is suppressed, setting the high-frequency characteristic to a design standard.