Nonvolatile semiconductor memory

A NAND-type flash memory comprising:

• first and second memory cells having a stack gate structure provided with a floating gate and a control gate and being adjacent to each other in an extending direction of the control gate;
• a first NAND cell unit having a first memory cell;
• and
• a second NAND cell unit having a second memory cell,
• wherein each of the floating gates of the first and second memory cells is comprised a first part, and a second part arranged on the first part, a width of the second part in an extending direction of the control gate being narrower than that of the first part,
• the first part is arranged between element isolation insulating layers with a stripe shape, and an upper surface of the element isolation insulating layer exists on the same position in height as the upper surface of the first part or on a lower position than the upper surface of the first part;
• and
• a first space between the first parts of the first and second memory cells is filled with one kind of an insulator, and the control gate is arranged at a second space between the second parts of the first and second memory cells via a dielectric material having a dielectric constant higher than a dielectric constant of the insulator;
• and
• the first part is also arranged on the upper surface of the element isolation insulating layer, and a width of the first part in an extending direction of the control gate is wider than that of the element isolation insulating layer.