A method of forming a silicon nitride film is described. According to the present invention, a silicon nitride film is deposited by thermally decomposing a silicon/nitrogen containing source gas or a silicon containing source gas and a nitrogen containing source gas at low deposition temperatures (e.g., less than 550.degree. C.) to form a silicon nitride film. The thermally deposited silicon nitride film is then treated with hydrogen radicals to form a treated silicon nitride film.