The invention relates to a semiconductor device, in particular to an interface optimized high-k gate dielectric complementary metal oxide semiconductor (CMOS) device. Interface layers with different thicknesses and different materials are adopted on a semiconductor substrate in an N-channel metal oxide semiconductor (NMOS) region and a semiconductor substrate of a P-channel metal oxide semiconductor (PMOS) region, the equivalent oxide thickness (EOT) of a device, in particular the EOT of a PMOS device, is effectively reduced, and the electron mobility of the device, in particular the electronmobility of an NMOS device is improved, so that the overall performance of the device is effectively improved.