In a solid state image sensor having two semiconductor substrates or more laminated longitudinally, electrical connection between the semiconductor substrates is made by a fine plug. An insulating film covering a first rear surface of a semiconductor substrate having a light receiving element, and an interlayer insulating film covering a second main surface of a semiconductor substrate mounting a semiconductor element are joined to each other. In its joint surface, a plug penetrating the insulating film and a lug embedded in a connection hole in an upper surface of the interlayer insulating film are joined, and the light receiving element and the semiconductor element are electrically connected through the plugs.