Semiconductor device with flash memory cells having improved arrangement for floating gate electrodes and control gate electrodes of the flash memory cells
A semiconductor device having a nonvolatile memory is reduced in size. In an AND type flash memory having a plurality of nonvolatile memory cells having a plurality of first electrodes, a plurality of word lines crossing therewith, and a plurality of floating gate electrodes disposed at positions which respectively lie between the plurality of adjacent first electrodes and overlap the plurality of word lines, as seen in plan view, the plurality of floating gate electrodes are formed in a convex shape, as seen in cross section, so as to be higher than the first electrodes. As a result, even when nonvolatile memory cells are reduced in size, it is possible to process the floating gate electrodes with ease. In addition, it is possible to improve the coupling ratio between floating gate electrodes and control gate electrodes of the word lines without increasing the area occupied by the nonvolatile memory cells.
1. A semiconductor device having a plurality of flash memory cells electrically connected to a word line extending to a first direction in plane view, comprising:
a plurality of floating gates formed over a semiconductor substrate;
a plurality of first insulating films formed between each floating gate in the first direction, respectively;
a second insulating film formed over a top surface of each of the first insulating films, side surfaces of each the floating gate and a top surface of each floating gate; and
a control gate configured to serve as the word line formed over the second insulating film,
wherein a height of the top surface of each of the floating gates is higher than a height of the top surface of each of the first insulating films,
wherein each of the first insulating films is formed in self-alignment with each of the floating gates,
wherein a length of each of the floating gates in a second direction being perpendicular to the first direction is larger than a maximum length of each of the floating gates in the first direction,
wherein a length from a top surface of the second insulating film which is formed over the first insulating films to the top surface of the floating gate is larger than a length of the space between each of the floating gates in the first direction, and larger than the length of each of the floating gates in the first direction,
wherein each of the floating gates includes a polysilicon film,
wherein the control gate includes a polysilicon film and a tungsten silicide film,
wherein each of the first insulating films includes a silicon oxide film, and
wherein the second insulating film includes a first silicon oxide film, a first silicon nitride film and a second silicon oxide film.