A method for forming a densified silicon oxynitride film with tensile stress and a semiconductor device including the densified silicon oxynitride film. The densified silicon oxynitride film can be formed by depositing a porous SiNC:H film on a substrate in a LPCVD process, and exposing the porous SiNC:H film to an oxygen-containing gas to incorporate oxygen into the SiNC:H film, thereby forming a densified SiONC:H film having a greater density than the porous SiNC:H film. The densified silicon oxynitride film can be included on a substrate including the semiconductor device.