A semiconductor package includes a substrate. A lower semiconductor chip is disposed above the substrate. An upper semiconductor chip is disposed on the lower semiconductor chip. A top surface of the lower semiconductor chip at an end of the lower semiconductor chip is exposed. A heat slug disposed above the upper semiconductor chip. A molding layer is disposed between the substrate and the heat slug. The molding layer is configured to seal the lower semiconductor chip and the upper semiconductor chip. An upper spacer is disposed between the lower semiconductor chip and the heat slug. The upper spacer is disposed on the exposed surface of the lower semiconductor chip.