A semiconductor device 100 comprises a silicon substrate 102, an N-type MOSFET 118 including a high concentration-high dielectric constant film 108b formed on the silicon substrate 102 and a polycrystalline silicon film 114, and a P-type MOSFET 120 including a low concentration-high dielectric constant film 108a and a polycrystalline silicon film 114 formed on the semiconductor substrate 102 to be juxtaposed to the N-type MOSFET 118. The low concentration-high dielectric constant film 108a and the high concentration-high dielectric constant film 108b are composed of a material containing one or more element (s) selected from a group consisting of Hf and Zr. The concentration of the above-described metallic element contained in the low concentration-high dielectric constant film 108a is lower than that contained in the high concentration-high dielectric constant film 108b.