Method of high density plasma CVD gap-filling

A gap filling process of depositing a film of SiO2 in gaps on a substrate by generating plasma in a process chamber by energizing gas containing silicon, oxygen and a heavy noble gas such as xenon or krypton. The gaps can have widths below 0.5 mu m and aspect ratios higher than 1.5:1. A substrate is supported on a substrate support wherein a gas passage supplies a temperature control gas into a space between opposed surfaces of the substrate and the substrate support, and the film is grown in the gaps on the substrate by contacting the substrate with the plasma. The silicon reactant can be SiH4 and the oxygen reactant can be pure oxygen gas supplied by O2/SiH4 ratio of