Provided is a capacitor that realizes a capacitance insulation film having a large relative permittivity and has sufficient capacitance even if an occupied space is small with a reduced amount of leakage current. A capacitor includes: a capacitance insulation film; and an upper electrode and lower electrode each formed on both sides of the capacitance insulation film. The capacitance insulation film is a complex oxide whose main ingredients are Zr, Al and O with the composition ratio of Zr to Al being set at (1−x): x (0.01≦x≦0.15) and is composed of a dielectric substance having a crystal structure. The lower electrode is composed of a conductor whose surface contiguous to at least the dielectric film has an amorphous structure.