In a semiconductor device formed by mounting a chip laminate including a semiconductor chip having a small diameter and a semiconductor chip having a large diameter over the top surface of a substrate, an excessive stress is prevented from being added to a joint of the two semiconductor chips. By mounting a first semiconductor chip having a large diameter over a support substrate and thereafter mounting a second semiconductor chip having a small diameter over the first semiconductor chip, it is possible to: suppress the inclination and unsteadiness of the second semiconductor chip mounted over the first semiconductor chip; and hence inhibit an excessive stress from being added to a joint of the first semiconductor chip and the second semiconductor chip.