A capacitor is provided that includes an electrostatic capacitance forming portion with a first electrode/dielectric layer/second electrode structure, and a silicon portion. Moreover, the silicon portion is disposed on at least a part of a side of the electrostatic capacitance forming portion. When the capacitor is viewed in a thickness direction thereof, a region occupied by the silicon portion in a lower portion of the electrostatic capacitance forming portion is 50% or less.