Nonvolatile semiconductor memory device and manufacturing method therefor

A manufacturing method of a nonvolatile semiconductor memory device, comprising:

• sequentially forming a first insulating film and a first conductive film in layer in a first gate-electrode area of a memory transistor on a semiconductor substrate and in a second gate-electrode area of a select gate transistor that is adjacent to the first gate-electrode area;
• removing the first conductive film and the first insulating film in the first gate-electrode area, and processing the first conductive film in a trapezoidal shape in the second gate-electrode area;
• sequentially forming a first oxide film, a nitride film, a second oxide film, and a second conductive film in the first and the second gate-electrode areas;
• exposing an upper surface of the first conductive film by etching the second conductive film, the second oxide film, the nitride film, and the first oxide film in a direction perpendicular to an in-plane direction of the semiconductor substrate to leave the second conductive film, the second oxide film, the nitride film, and the first oxide film in an area on an inclined plane of the first conductive film that is processed in the trapezoidal shape and in the first gate-electrode area;
• forming a third conductive film that connects the first conductive film and the second conductive film, in the second gate-electrode area;
• forming a memory cell that has a first oxide film, a nitride film, a second oxide film, and a second conductive film in this sequence on the semiconductor substrate by etching the second oxide film, the nitride film, and the first oxide film in the first gate-electrode area in a direction perpendicular to an in-plane direction of the semiconductor substrate to perform patterning, and then forming an end surface thereof on a side of the first gate-electrode area by etching the second conductive film, the second oxide film, the nitride film, and the first oxide film in the direction perpendicular to the in-plane direction of the semiconductor substrate at a position on the inclined plane of the first conductive film to leave the second conductive film, the second oxide film, the nitride film, and the first oxide film on the inclined plane of the first conductive film;
• and
• forming a gate electrode of the select gate transistor that has the first insulating film, the first conductive film, the first oxide film and the nitride film and the second oxide film and the second conductive film that are layered on the inclined plane of the first conductive film, and the third conductive film that connects the first conductive film and the second conductive film by forming an end surface on an opposite side to the first gate-electrode area by etching the third conductive film, the first conductive film, and the first insulating film in the direction perpendicular to the in-plane direction of the semiconductor substrate to leave a portion of the third conductive film at which the first conductive film and the second conductive are connected.