An interposer according to an embodiment of the present invention includes a base layer having opposite first and second surfaces, a wiring structure on the first surface of the base layer, an interposer protective layer disposed on the second surface of the base layer and having a pad recess with a lower surface of the interposer protective layer positioned at a first vertical level and a bottom surface of the pad recess positioned at a second vertical level that is higher than the first vertical level, an interposer pad of which a portion fills the pad recess of the interposer protective layer and the remaining portion protrudes from the interposer protective layer, and an interposer through electrode extending through the base layer and the interposer protective layer to the interposer pad, the interposer through electrode electrically connecting the wiring structure to the interposer pad.