A capacitor includes metallic tantalum and a dielectric layer. The dielectric layer covers the metallic tantalum and includes a tantalum oxide. The dielectric layer includes fluorine and phosphorus. The dielectric layer includes, for example, a first portion and a second portion. The first portion is a portion separated from the metallic tantalum in a thickness direction of the dielectric layer. The second portion is a portion in contact with the metallic tantalum in the thickness direction of the dielectric layer.