Semiconductor memory device and manufacturing method thereof

摘要

A semiconductor-memory device that reduces leak off due to miniaturization of memory cells, and comprises as a single unit cell: a substrate 1 having a trench section 1 a; a selector gate 3 that is located via an insulating film 2 on the substrate adjacent to the trench section 1 a; a first well 1 b that is formed on the surface of the substrate 1 below the selector gate 3 ; a floating gate 6 that is located via an insulating film 8 a on the surface of the bottom section and sidewall section of the trench section 1 a; a second well 1 c that is formed on the surface of the bottom section of the trench section 1 a below the floating gate 6 ; a first diffusion area 7 a that is formed on the surface of the bottom section of the trench section 1 a; and a control gate 11 located via an insulating film 8 on top of the floating gate 6 ; and where the area near the sidewall surface and bottom surface of the trench section 1 a forms a channel in the selector gate 3 ; and the impurity density of the first well 1 b is not more than the impurity density of the second well 1 c.