To prevent the deterioration of device characteristics by preventing the configuring atoms of a high dielectric film in a process from scattering.

In a nonvolatile semiconductor storage device 100 in which a memory cell 110 and a transistor 120 are formed on a silicon substrate 101, at least a sidewall 127 covering the side face of a high dielectric film 124 is formed across a lower gate 122 and a silicon gate 126 on the side face of a laminate film 120T configuring the transistor 120. As the materials of the sidewall 127, a conductor for preventing the configuring atoms of the high dielectric film 124 such as SiGe from scattering is used.