A method of forming a semiconductor device includes providing a substrate for the semiconductor device. A base oxide layer is formed overlying the substrate by applying a rapid thermal oxidation (RTO) of the substrate in the presence of oxygen. A nitrogen-rich region is formed within and at a surface of the base oxide layer. The nitrogen-rich region overlies an oxide region in the base oxide layer. Afterwards, the semiconductor device is annealed in a dilute oxygen and hydrogen-free ambient of below 1 Torr partial pressure of the oxygen. The annealing heals bond damage in both the oxide region and the nitrogen-rich region in the base oxide layer. After annealing the semiconductor device in the dilute oxygen ambient, in-situ steam generation (ISSG) is used to grow and density the oxide region in the base oxide layer at an interface between the substrate and base oxide layer.