of tungsten which has initially been formed the partial pressure of silane is typically in the range from 1 to 30 mtorr more typically about 1 mtorr giving a silane tungsten hexafluoride ratio of around 0 5 throughout the tungsten deposition process the ambient temperature should be in the range 200 u00b0 to 300 u00b0 c typically a via formed on a capping layer of titanium or titanium nitride in accordance with the present invention has a specific contact resistivity of up to 2 5 u00d7 10 8 ohms cm 2 more preferably the specific contact resistivity being from 1 0 u00d7 10 9 to 1 2 u00d7 10 8 ohms cm 2 this can be contrasted with a substantially open circuit contact resistance of a tungsten contact on an aluminium interconnect layer which is measured at a potential which is sufficiently low so as not to break down the dielectric insulating aluminium compound such as aluminium oxide and or aluminium fluoride at the interface between the tungsten and the aluminium when the capping layer is titanium or itanium nitride any titanium fluoride which is formed during the selective deposition of the contact is removed as a result of its volatility and so substantially no residual fluorides are left on the capping layer beneath the contact to raise the resistivity of the contact in addition.