for example two layers first a layer of titanium is deposited and then a layer of titanium nitride is deposited or first a layer of titanium is deposited and then a layer of titanium tungsten is deposited when the opening 54 is a dielectric contact the barrier layer 60 comprises for example either titanium nitride or titanium tungsten the thickness of the barrier layer 60 is decided by the aspect ratio of the opening after the barrier layer 60 is deposited it is processed either by a thermal treatment or by being cooled in the air for a period of time in order to increase the insulating effect of the barrier layer 60 please refer to 3 c based on the steps shown in 3 b a pre in situ metal layer 62 is deposited on barrier layer 60 the pre in situ metal layer can be composed of titanium or titanium tungsten or titanium nitride titanium nitride is preferable the thickness of the layer for example is about 50 angstroms to about 1 100 angstroms the pre in situ metal layer 62 is neither processed with a thermal treatment nor is it cooled in the air for a period of time it provides a suitable deposition surface so long as the pre in situ metal layer is deposited the function of reducing metal etching residues on conducting structure layer fulfilled please refer to 3 d in the same vacuum device where the pre in situ metal layer 62 is deposited and under continuous vacuum condition a metal layer 64 is deposited on the pre in.