A semiconductor package includes a substrate and a semiconductor chip disposed over the substrate. The substrate includes: a base layer including an upper surface facing the semiconductor chip; an upper ground electrode plate disposed over the upper surface of the base layer and configured to transmit a ground voltage to the semiconductor chip; and a dummy power pattern disposed in the upper ground electrode plate and having a side surface which is surrounded by the upper ground electrode plate and is spaced apart from the upper ground electrode plate with an insulating material between the dummy power pattern and the upper ground electrode plate. A ground voltage transmission path from the upper ground electrode plate to the semiconductor chip is spaced apart from the dummy power pattern.