A semiconductor device and a manufacturing method thereof are provided. The manufacturing method includes following steps. A mold is provided. The mold has a chamber and a plurality of protrusions in the chamber. A thermosetting material is injected into the chamber. The thermosetting material is cured. A parting step is performed to separate the cured thermosetting material from the mold, so as to form an interposer substrate. A plurality of blind holes corresponding to the protrusions is formed on the interposer substrate. A conductive material is filled into the blind holes to form a plurality of conductive pillars. A conductive pattern layer is formed on a surface of the interposer substrate. The conductive pattern layer is electrically connected with the conductive pillars.