Nonvolatile semiconductor memory device and method of manufacturing the same

A method of manufacturing a nonvolatile semiconductor memory device, the nonvolatile semiconductor memory device including a plurality of memory strings each having a plurality of electrically rewritable memory cells connected in series, comprising:

• depositing a plurality of first conductive layers on a substrate;
• penetrating the plurality of first conductive layers to form a penetration hole;
• forming a charge storage layer on a side surface of the penetration hole;
• forming a semiconductor layer so as to fill the penetration hole;
• forming a stepped portion formed in a stepped shape in the plurality of first conductive layers such that positions of ends of the plurality of first conductive layers differ from one another;
• and
• forming a plurality of second conductive layers extending upwardly from an upper surface of the first conductive layers configuring the stepped portion,
• the plurality of second conductive layers being formed such that upper ends thereof are aligned with a surface parallel to the substrate, and such that a diameter thereof decreases from the upper end thereof to a lower end thereof, and being formed such that the greater a length thereof in the perpendicular direction, the larger a diameter of the upper end thereof.