A highly tensile dielectric layer is generated on a heat sensitive substrate while not exceeding thermal budget constraints. Ultraviolet (UV) irradiation is used to produce highly tensile films to be used, for example, in strained NMOS transistor architectures. UV curing of as-deposited PECVD silicon nitride films, for example, has been shown to produce films with stresses of at least 1.65 E10 dynes/cm2. Other dielectric capping layer film materials show similar results. In transistor implementations, the stress from a source/drain region capping layer composed of such a film is uniaxially transferred to the NMOS channel through the source-drain regions to create tensile strain in the NMOS channel.