In a method of manufacturing a semiconductor device having a buried wiring
structure of copper, a conductive barrier film 17a of buried second layer
wirings L2 is protected against oxidation upon forming an insulative film
15b for a wiring cap with an SiON film formed by a plasma CVD method using
a gas mixture, for example, of a trimethoxysilane gas and a nitrogen
oxidized gas, whereby the dielectric breakdown strength between wirings of
copper as the main conductor layer of the semiconductor device can be
improved.
