An object of the present invention is to improve the performance of a semiconductor device having a CMISFET. Each of an n channel MISFET and a p channel MISFET which form the CMISFET includes a gate insulating film composed of a silicon oxynitride film and a gate electrode including a silicon film positioned on the gate insulating film. Metal elements such as Hf are introduced near the interface between the gate electrode and the gate insulating film with a surface density of 1×1013 to 5×1014 atoms/cm2. The impurity concentration of channel regions of the n channel MISFET and the p channel MISFET is controlled to be equal to or lower than 1.2×1018/cm3.