Patent ID: 8043930

Claim:
A semiconductor memory device manufacturing method comprising: in a semiconductor substrate having a first region and a second region, forming a first gate insulating film on the semiconductor substrate in the first region and forming a second gate insulating film on the semiconductor substrate in the second region; forming a first gate wiring material on the first gate insulating film and the second gate insulating film; forming a first element isolation insulating film by partially removing the first gate wiring material, the first gate insulating film, and the semiconductor substrate and forming a second element isolation insulating film by partially removing the first gate wiring material, the second gate insulating film, and the semiconductor substrate; making a first height from an upper surface of the semiconductor substrate to an upper surface of the first element isolation insulating film smaller than a second height from the upper surface of the semiconductor substrate to an upper surface of the second element isolation insulating film by removing an upper portion of the first element isolation insulating film; forming a second gate wiring material in the first region; forming a third gate wiring material on the second gate wiring material, the first gate wiring material in the second region and the second element isolation insulating film; forming a mask layer on the third gate wiring material to make an upper surface of the mask layer in the first region higher than an upper surface of the mask layer in the second region; and removing an upper portion of the mask layer in the first region to make a film thickness of the mask layer in the first region thinner than a film thickness of the mask layer in the second region to make a height from the upper surface of the semiconductor substrate to the upper surface of the mask layer in the first region equal to a height from the upper surface of the semiconductor substrate to the upper surface of the mask layer in the second region.