To let a semiconductor device have such a structure as not to have a base plate for supporting a semiconductor constitutional body and an insulation layer, in the semiconductor device having the insulation layer including an upper-layer insulation film in the periphery and the upside of the semiconductor constitutional body named as CSP.

The manufacturing method of the semiconductor device has in succession a process for disposing a semiconductor constitutional body 1 on a metal base plate 51, a process for forming an insulation layer 23 including an upper-layer insulation film 27, on the top surface of the base plate 51 present in the periphery of the semiconductor constitutional body 1, and on the upside of the base plate 51 and the body 1, a process for disposing on the top surface of the upper-layer insulation film 27 a warp preventing plate 55 made of the same material as the metal base plate 51, and a process for removing the base plate 51 and the warp preventing plate 55 therefrom. In this way, since the base plate 51 is removed, the semiconductor device can be thinned by the part thereof.

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