There is provided a nonvolatile semiconductor memory device, including, a tunnel insulator, a floating gate electrode including a first floating gate electrode and a second floating gate electrode being constituted with a nondegenerate state semiconductor, an intergate insulating film formed to cover at least continuously an upper and a portion of a side surface of the floating gate electrode, and a control gate electrode in order, and an isolation insulating film, a lower portion of the isolation insulating film being embedded in the semiconductor substrate in both sides of the floating gate electrode along a channel width direction, an upper portion of the isolation insulating film contacting with a side surface of the first floating gate electrode and protruding to a level between an upper surface of the semiconductor substrate and an upper surface of the first floating gate electrode.