A semiconductor device and a method of manufacturing same may include a stack including alternately stacked conductive layers and insulating layers, a separation insulating structure passing through the stack, and including a line pattern, first protrusion patterns protruded from the line pattern to one side, and second protrusion patterns protruded from the line pattern to another side, first channel structures passing through the stack at the one side of the separation insulating structure and surrounding the first protrusion patterns, respectively, and second channel structures passing through the stack at the another side of the separation insulating structure and surrounding the second protrusion patterns, respectively.