Abstract: A method of fabricating CMOS integrated circuits including the ordered steps of: depositing a layer of phosphorus doped silicon oxide; heating the oxide layer at a temperature and duration sufficient to reflow and densify it; forming contact apertures in the oxide layer for exposing source and drain regions of transistors; and cleaning the wafer in an etchant solution for rounding off sharp edges on the oxide layer prior to contact metallization. In a preferred embodiment, all steps between forming contact apertures and through metallization are formed at a temperature that is lower than the temperature that will cause flow of the oxide layer.