A densified dielectric film is formed on a substrate by a process that involves annealing a film deposited on the substrate by application of a localized energy pulse, such as a laser pulse, for example one of about 10 to 100 ns in duration from an excimer laser, that raises the temperature of the film above 1000.degree. C. without raising the substrate temperature sufficiently to modify its properties (e.g., the substrate temperature remains below 550.degree. C. or preferably in many applications below 400.degree. C.). The dielectric deposition may be by any suitable process, for example CVD, SOG (spin-on glass), ALD, or catalyzed PDL. The resulting film is densified without detrimentally impacting underlying substrate layers. The invention enables dielectric gap fill and film densification at low temperature to the 45 nm technology node and beyond, while maintaining oxide film properties.