Means for Solution: This interposer (10) comprises the silicon substrate (12), a plurality of through-hole conductors (20) formed on the above-described silicon substrate, and a capacitor (15) formed with the upper electrodes (14) and the lower electrodes (18) formed by extending the land portions of the above-described through-hole conductors and the dielectric layer (16) formed between the both electrodes. The rewiring layers (23-1, 23-2) formed as desired are formed on the layers other than the above-described capacitor layer.