A method of depositing doped silicon dioxide layers in the fabrication of semiconductor devices has been found. This method entails the reaction of a mixture of silane, nitrous oxide and a source of a dopant, e.g., phosphine or diborane. The reaction is performed at relatively high temperature, typically between 800 and 900 degrees C., and excellent step coverage is obtained. Further, the pinhole problems previously associated with high temperature techniques are avoided. Lower dopant concentrations, e.g., below 6%, are also practical.