A package on package structure includes a lower package and an upper package. The lower package includes a first semiconductor chip disposed in a chip region of an upper surface of a first substrate. The upper package includes a second semiconductor chip disposed on an upper surface of a second substrate, and a decoupling capacitor disposed in an outer region of a lower surface of the second substrate. The lower surface of the second substrate opposes the upper surface of the second substrate and faces the upper surface of the first substrate. The plane area of the second substrate is larger than the plane area of the first substrate. The outer region of the lower surface of the second substrate extends beyond a periphery of the first substrate.