SEMICONDUCTOR DEVICE WITH IMPROVED COUPLING BETWEEN CONTACT PLUG AND PLUG THEREON AND MANUFACTURING METHOD THEREOF

PURPOSE: A semiconductor device and a manufacturing method thereof are provided to improve characteristics of a semiconductor device by improving a coupling between a contact plug connected to a semiconductor substrate and a plug connected to an upper surface of the contact plug. CONSTITUTION: A first gate insulating film and a first gate electrode are formed on a semiconductor substrate(100). A first gate insulating film and a second gate electrode are formed on the semiconductor substrate and are disposed to be extended in parallel with an extending direction of the first gate insulating film and the first gate electrode. A first insulating film is formed to cover the first gate insulating film and a surface of the first gate electrode. A second insulating film is formed to cover the second gate insulating film and a surface of the second gate electrode. A contact plug(17a,17b) is connected to a dopant diffusion region of the semiconductor substrate within a contact hole. Surfaces of the first insulating film and the second insulating film are formed in the contact hole. An area of the contact plug in a direction parallel to a main surface of the semiconductor substrate is larger on an upper surface than on a lower surface.