A semiconductor device includes wiring boards each having an insulating board, conductor circuits and through-holes, the insulating board having top and bottom surfaces, the conductor circuits formed on the top and bottom surfaces, the through holes penetrating the insulating board and electrically connecting the conductor circuits of the top and bottom surfaces; conductor posts each having flange, head and leg portions, the flange portion having first and second surfaces and having an external diameter larger than that of the through-hole, the head portion protruding from the first surface, the leg portion protruding from the second surface; and electronic components each having an electrode formed on one or more surfaces and connected to the leg portion. The head portion is inserted until the first surface of the flange portion comes into contact with the bottom surface of the wiring board and electrically connected at an inner wall of the through-hole.