To mount electronic circuits in high density on a circuit device by forming, in a substrate, connection electrodes for connecting each of inner electrodes to either one of a plurality of ground electrodes.

On the outer surface of a ceramic substrate 2, a plurality of signal lines 3 are formed in parallel with the each other in the longitudinal direction of the ceramic substrate 2. One end part 3a of each of the signal lines 3 is formed near a front end part 2c of the ceramic substrate 2. The other end part 3b of each signal line 3 formed on a rear end face 2d and a lower face 2b of the substrate 2 also serves for an electrode used for surface mounting of a filter 1 on a circuit device such as a LAN card. In a part of the lower face 2b of the substrate 2 closer to the rear end face 2d, a plurality of circular ground electrodes 4 are formed, a plurality of cylindrical connection electrodes 6 for connecting each of the ground electrodes 4 to the inner electrode 5 are formed in the ceramic substrate 2.