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 C.sub.5 F.sub.8, C.sub.3 F.sub.6, or C.sub.4 F.sub.6 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.
