Nonvolatile semiconductor memory device and its manufacturing method

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

• forming a first insulating film on a semiconductor substrate having a first upper surface;
• forming a first electrode material film on the first insulating film;
• etching the first electrode material, the first insulating film, and the semiconductor substrate so as to form a groove in the semiconductor substrate;
• embedding a second insulating film in the groove and forming an isolation portion so that an upper portion of the isolation portion protrudes from the first upper surface;
• forming a second electrode material film on the first electrode material and the isolation portion;
• etching the second electrode material film and the upper portion of the isolation portion so that a pair of inner side surfaces of the isolation portion face to a whole side surface of the first electrode material film via the isolation portion;
• forming a third insulating film on the second electrode material film and the pair of inner side surfaces of the isolation portion;
• and
• forming a control gate on the third insulating film and between the pair of inner side surfaces of the isolation portion.

A method for manufacturing a nonvolatile semiconductor memory device including a semiconductor substrate having a first upper surface, a plurality of element isolation films embedded in and protruding from the semiconductor substrate, having an upper portion being higher than the first upper surface and a first side surface, a first gate insulating film formed on the first upper surface between the element isolation films, and a floating gate formed on the first gate insulating film and having a second upper surface being higher than the first upper surface and a second side surface contacted with the first side surface, the method comprising:

• forming a recess in the upper portion of the element isolation film so that a pair of inner side surfaces of the recess face to the whole second side surface of the floating gate via the element isolation film;
• forming a second gate insulating film on the second upper surface of the floating gate and the pair of inner side surfaces of the recess;
• and
• forming a control gate on the second gate insulating film and between the pair of inner side surfaces of the recess.

A method for manufacturing a nonvolatile semiconductor memory device including a semiconductor substrate having a first upper surface, a plurality of element isolation films embedded in and protruding from the semiconductor substrate, having a first side surface, a first gate insulating film formed on the first upper surface between the element isolation films, and a floating gate formed on the first gate insulating film and having a second side surface contacted with the first side surface, the method comprising:

• etching an upper portion of the element isolation film so that a pair of inner side surfaces of the element isolation film face to the whole second side surface of the floating gate via the element isolation film;
• forming a second gate insulating film on the second upper surface of the floating gate and the pair of inner side surfaces of the recess;
• and
• forming a control gate on the second gate insulating film and between the pair of inner side surfaces of the recess.