A dual-strained Si and SiGe FinFET device with dielectric isolation and a dual-strained nanowire device and methods of forming them are provided. Embodiments include a SiGe SRB formed on a silicon substrate, the SRB having a first region and a second region; a first and a second dielectric isolation layer formed on the first region and on the second region of the SiGe SRB, respectively; a tensile strained Si fin formed on the first dielectric isolation layer; a compressive strained SiGe fin formed on the second dielectric isolation layer; first source/drain regions formed at opposite sides of the tensile strained Si fin; second source/drain regions formed at opposite sides of the compressive strained SiGe fin; a first RMG formed between the first source/drain regions; and a second RMG formed between the second source/drain regions.