Methods of manufacturing a semiconductor device include forming an NMOS transistor on a semiconductor substrate, forming a first interlayer dielectric layer on the NMOS transistor, and dehydrogenating the first interlayer dielectric layer. Dehydrogenating the first interlayer dielectric layer may change a stress of the first interlayer dielectric layer. In particular, the first interlayer dielectric layer may have a tensile stress of 200 MPa or more after dehydrogenization. Semiconductor devices including dehydrogenated interlayer dielectric layers are also provided.