A device for processing electromagnetic waves in the microwave range, with a body provided with a circuit element which is electrically connected to a strip-type transmission line which comprises conductor tracks, said body being mechanically connected to an insulating substrate via contact bodies. The transmission line is formed by conductor tracks which lie on mutually facing surfaces of the body and the insulating substrate, respectively. The transmission line in the device is present between the body and the insulating substrate, the contact bodies providing a separation between the conductor tracks. Thus, it is not necessary then to use a second side of the body remote from the insulating substrate for the manufacture of transmission lines.