Contact hole filling in a semiconductor device by irradiation with plasma of inert gas ions

A hole fill method of filling contact holes formed in an interlayer isolation layer laid on a substrate of a semiconductor device having a principal surface and sidewalls defining said contact holes, said hole fill method including steps of laying on said principal surface and on said sidewalls a covering film of a covering material consisting essentially of aluminum and of heating said covering film for reflow of aluminum of said covering material into said contact holes to spread a conductor film covering said principal surface and filing said contact holes, wherein said hole fill method comprises a step of irradiating, after said film laying step, said covering film with plasma of inert gas ions to remove an aluminum oxide film formed on said covering film, and wherein said inert gas ions have an energy below 100 electron volts and a density calculated to cause removal of said aluminum oxide film while avoiding incorporation of said inert gas ions into said covering film.