<p>To provide a method for forming insulating thin films that can induce condensation of silanol and dehydration to a high degree at or near ambient pressure. An interlevel dielectric layer is formed on a semiconductor substrate by coating hydrogen silsesquioxane resin onto the substrate and curing the hydrogen silsesquioxane resin to produce an interlevel dielectric layer. This interlevel dielectric layer is then heated at a pressure from 1 to 1,000 torr at a temperature from 150 to 550 DEG C</p>