A method of manufacturing a non-volatile memory device includes forming a first conductive layer over a tunnel dielectric layer that is provided on a semiconductor substrate. A non-conductive layer is formed over the first conductive film. The non-conductive layer is etched to define a stack structure between first and second trenches, the stack structure including the first conductive layer and the non-conductive layer. A second conductive layer is formed over the stack structure and into the first and second trenches. An upper portion of the second conductive layer is etched to expose the non-conductive layer of the stack structure. The non-conductive layer of the stack structure is removed to form a three-dimensional (3-D) floating gate with an opening, the floating gate including the first and second conductive layers. A third conductive layer is provided within the 3-D floating gate via the opening of the 3-D floating gate to form a control gate.