The invention relates to the technical field of semiconductor manufacturing, and particularly relates to a semiconductor device and a semiconductor device manufacturing method. Through sequentially manufacturing a SiGe layer and a TiN layer in a core device area and an interlayer dielectric layer between a subsequently-manufactured sample gate and a substrate and forming a sample gate structure with a side wall and an interlayer dielectric thin film in the dielectric layer, the sample gate, the SiGe layer and the TiN layer are removed sequentially, a chemical oxidation process is adopted to manufacture a gate oxide thin film and a metal gate located on the thin film in the core device area, and thus, the EOT (Equivalent Oxide Thickness) size of the formed device structure meets process requirements. As the above side walls and the interlayer dielectric thin film are not damaged when the SiGe layer and the TiN layer are removed, integrity of the subsequently-manufactured metal gate structure is further ensured, and the performance and the yield of the finally-manufactured device are greatly improved.