A trench-fill material is deposited to fill a trench in a substrate disposed in a process chamber. An inert gas is introduced into the process chamber and a plasma is formed to heat the substrate to a preset temperature, which is typically the temperature at which deposition of the trench-fill material is to take place. The plasma is terminated upon reaching the preset temperature for the substrate. A process gas is then flowed into the process chamber without plasma excitation until the process gas flow and distribution achieve a generally steady state in the process chamber. A plasma is then formed to deposit the trench-fill material on the surface of the substrate and fill the trench. By establishing generally steady state conditions in the chamber prior to deposition, transient effects are reduced and more uniform deposition of the trench-fill material is obtained. The step of forming the plasma typically includes coupling source plasma energy into the process chamber at a total power density of at least about 15 Watts/cm 2 .