A substrate for a semiconductor package comprises a dielectric substrate, a circuit pattern, and an electromagnetic band gap (EBG) pattern. The circuit pattern is formed on a first surface of the dielectric substrate and is connected to ground via a ground connection. The electromagnetic band gap (EBG) pattern comprises a plurality of zigzag unit structures formed on a second surface of the dielectric substrate, wherein the second surface is formed on an opposite side of the dielectric substrate from the first surface; the zigzag unit structures are electrically connected to each other; and at least one of the zigzag unit structures is electrically connected to the ground connection.