There is provided a trap memory device suppresses electric charges from flowing from the outside into a charge accumulation region and accumulated electric charges from diffusing to the outside or flowing out due to a defect. A gate conductor 6 is formed through a laminate insulating film including a first gate insulating film 3, a charge accumulation layer 4 and a second gate insulating film 5 on a silicon substrate 1. The laminate insulating film (3 to 5) projects outside the gate conductor 6 and extends to under the outer end of a side wall 8. The charge accumulation layer 4 includes a high trap surface-density region 4a immediately under the gate conductor and a low trap surface-density region 4b outside the gate conductor.