Flash memory device and method of fabricating the same
View Patent ↗A flash memory device includes control gates that are formed to completely surround the top and sides of floating gates. The control gates are located between the floating gates that are adjacent in the word line direction as well as the floating gates that are adjacent in the bit line direction. The present flash memory device reduces a shift in a threshold voltage resulting from interference among floating gates and increases an overlapping area of the floating gate and the control gates. Thus, there is an effect in that the coupling ratio can be increased.
1. A method of fabricating a flash memory device, the method comprising:
forming a tunnel dielectric film on a semiconductor substrate in which an active region and a field region are defined by isolation films;
forming floating gates, which are separated in an island shape on a cell basis, over the active region and the field region adjacent to the active region;
forming an interlayer dielectric film over a resulting surface;
forming an electrode material over the interlayer dielectric film;
forming a hard mask film pattern over a predetermined region of the electrode material;
forming a hard mask spacer at the sides of the hard mask film pattern, and
patterning the electrode material to form control gates that surround the top and sides of the floating gates using the hard mask film pattern and the hard mask spacer as masks.
2. The method as claimed in claim 1 , wherein the hard mask film and the hard mask spacer are formed of an oxide film.
3. The method as claimed in claim 1 , further comprising:
performing a re-oxidization process for mitigating etch damage after the control gates are formed.
4. The method as claimed in claim 1 , wherein the tunnel dielectric film is formed using an oxide film, and the interlayer dielectric film is formed using an oxide film or a stack film comprising an oxide film and a nitride film.
5. The method as claimed in claim 1 , wherein the floating gates and the control gates are formed using polysilicon or a metal compound.
6. The method as claimed in claim 1 , wherein a width of the control gates in a second direction is perpendicular to a first direction, wherein the floating gates overlap the isolation films in the first direction, the width of the control gates being substantially equal to the sum of: a width of the floating gates in the second direction, twice a thickness of the interlayer dielectric film, and an overlay margin.
7. The method as claimed in claim 1 , wherein the floating gates are formed in the shape of one of: a square, a circle, an ellipse or a polygon.