An interposer substrate having electrodes on the front surface and on the rear surface thereof, respectively, is prepared, and at least one memory chip having electrodes connected to an internal circuit is prepared. Then, the rear surface of the memory chip is bonded to the front surface of the interposer substrate, and the memory chip is sealed to the front surface of the interposer substrate to constitute an encapsulated capsule type semiconductor package. On the other hand, a logic chip is prepared. Further, a main substrate is prepared in which electrodes are formed on the front surface and on the rear surface, respectively, and desired internal connections are provided between these electrodes. Then, the capsule type semiconductor package and the logic chip are laminated on the main substrate, and desired connections are provided between the electrodes on the rear surface of the interposer substrate of the capsule type semiconductor package, the electrodes of the logic chip and the electrodes on the front surface of the main substrate. The capsule type semiconductor package and the logic chip are sealed to the front surface of the main substrate by a resin to obtain a system-in-package type semiconductor device.