A plurality of metal interconnections are formed on a semiconductor substrate. The semiconductor substrate is held on a sample stage in a reactor chamber of a plasma processing apparatus and a material gas containing C5F8, C3F6, or C4F6 as a main component is introduced into the reactor chamber, so that a first fluorine-containing organic film having cavities at positions between the metal interconnections is deposited between the metal interconnections and on the top surfaces of the metal interconnections.