Solid electrolytic capacitor and manufacturing method

The purpose of the present invention is to provide a solid electrolytic capacitor that achieves both low ESR and high withstand voltage. The solid electrolytic capacitor comprises a positive electrode foil, a negative electrode body, and a capacitor element having an electrolyte. In the positive electrode foil, the surface is enlarged with tunnel-shaped etching pits, and there is a dielectric film on the surface. The negative electrode body faces the positive electrode foil. The electrolyte includes a solid electrolyte layer that contains a conductive polymer. This solid electrolyte layer has a weight of 250 mg/cm3 or less per unit volume of the capacitor element.