An interposer integrated with capacitors (100) includes a plug substrate (10) in which via-plugs (12) is formed, and a capacitor substrate (20) in which capacitors are formed. The capacitor substrate (20) includes a substrate body (21), capacitors (22) formed on the main surface of the substrate body, a cover insulating film (25) that covers the capacitors, a terminal electrodes (26) connected to the electrodes of the capacitor and formed on the cover insulating film, electrode pads (24) formed on the rear surface of the substrate body, and via-plugs 23 connecting together the terminal electrodes and electrode pads. The plug substrate (10) includes a substrate body (11), and electrode pads (13) formed on the main surface of the substrate body corresponding to the terminal electrodes of the capacitor substrate, and via-plugs (12) penetrating the substrate body and connected to the electrode pads.