A circuit device having differently-strained NMOS and PMOS FinFETs is provided. In an exemplary embodiment, a semiconductor device includes a substrate with a first fin structure and a second fin structure formed thereup. The first fin structure includes opposing source/drain regions disposed above a surface of the substrate; a channel region disposed between the opposing source/drain regions and disposed above the surface of the substrate; and a first buried layer disposed between the channel region and the substrate. The first buried layer includes a compound semiconductor oxide. The second fin structure includes a second buried layer disposed between the substrate and a channel region of the second fin structure, such that the second buried layer is different in composition from the first. For example, the second fin structure may be free of the compound semiconductor oxide.