The semiconductor package including a first semiconductor package including a first semiconductor package substrate, and a first semiconductor chip on the first semiconductor package substrate, an interposer disposed on the first semiconductor package is provided. Interposer electrically connects the first semiconductor package with an external semiconductor package, and has first and second sides opposed to each other. The second side is located between the first side and the first semiconductor package substrate, a first recess is formed in the second side of the interposer. The first recess has side walls extended from the second side toward the first side of the interposer and an upper surface connected to the side walls and the upper surface of the first recess faces the first semiconductor chip and a via in the interposer. The via does not transmit an electrical signal between the first semiconductor package and the external semiconductor package.