Provided are a semiconductor device including an interposer having a relatively thin thickness without a through silicon via and a method of manufacturing the same. The method of manufacturing a semiconductor device includes forming an interposer including a redistribution layer and a dielectric layer on a dummy substrate, connecting a semiconductor die to the redistribution layer facing an upper portion of the interposer, encapsulating the semiconductor die by using an encapsulation, removing the dummy substrate from the interposer, and connecting a bump to the redistribution layer facing a lower portion of the interposer.