US Patent 9548303 FinFET devices with unique fin shape and the fabrication thereof

A semiconductor device includes a PMOS FinFET and an NMOS FinFET. The PMOS FinFET includes a substrate, a silicon germanium layer disposed over the substrate, a silicon layer disposed over the silicon germanium layer, and a PMOS fin disposed over the silicon layer. The PMOS fin contains silicon germanium. The NMOS FinFET includes the substrate, a silicon germanium oxide layer disposed over the substrate, a silicon oxide layer disposed over the silicon germanium oxide layer, and an NMOS fin disposed over the silicon oxide layer. The NMOS fin contains silicon. The silicon germanium oxide layer and the silicon oxide layer collectively define a concave recess in a horizontal direction. The concave recess is partially disposed below the NMOS fin.