Nonvolatile memory device and method of fabricating the same

1. A nonvolatile memory device comprising:

a semiconductor substrate;

a source region that is formed in the semiconductor substrate;

a gate insulating film that is formed so as to partially overlap the source region on the semiconductor substrate;

a floating gate that is formed on the gate insulating film so as to have a first side edge that is substantially straight so as to form a portion of uniform width overlap the source region and having a second side opposite the first side that has a convex curvature, whereby a uniform electric field is formed in the portion that overlaps the source region;

a control gate that is formed so as to be electrically isolated along one side of the floating gate from an upper part of the floating gate;

an inter-gate insulating film that is interposed between the floating gate and the control gate; and

a drain region that is formed so as to be adjacent the other side of the control gate.

2. The nonvolatile memory device of claim 1 , wherein a thickness of the inter-gate insulating film gradually becomes thinner from a center toward both ends.

3. A nonvolatile memory device comprising:

a semiconductor substrate;

a common source region that is formed in the semiconductor substrate;

first and second gate insulating films that are formed on both sides of the common source region so as to partially overlap the common source region;

first and second floating gates that are formed on the first and second gate insulating films, respectively, wherein each of the first and second floating gates has a first side edge that is substantially straight so as to form respective portions of uniform width overlapping the common source region and each having a second side opposite the first side that has a convex curvature, whereby a uniform electric field is formed in the floating gate portions overlapping the common source region;

first and second control gates that are formed so as to be electrically isolated along the other side of the floating gate from an upper part of the first and second floating gates toward a direction opposite to the common source region, respectively;

first and second inter-gate insulating films that are formed on the first and second floating gates and interposed between the first and second floating gates and the first and second control gates; and

first and second drain regions that are formed so as to be adjacent the other side of the first and second control gates, respectively.

4. The nonvolatile memory device of claim 3 , wherein a thickness of each of the first and second inter-gate insulating films gradually becomes thinner from a center toward both ends.