A method for forming a silicon germanium oxide thin film on a substrate in a reaction space may be performed using an atomic layer deposition (ALD) process. The process may include at least one cycle comprising a germanium oxide deposition sub-cycle and a silicon oxide deposition sub-cycle. The germanium oxide deposition sub-cycle may include contacting the substrate with a germanium reactant, removing excess germanium reactant, and contacting the substrate with a first oxygen reactant. The silicon oxide deposition sub-cycle may include contacting the substrate with a silicon reactant, removing excess silicon reactant, and contacting the substrate with a second oxygen reactant. The films of the present disclosure exhibit desirable etch rates relative to thermal oxide. Depending on the films' composition, the etch rates may be higher or lower than the etch rates of thermal oxide.