A semiconductor memory device has a plurality of core chips and an interface chip, whose specification can be easily changed, while suppressing the degradation of its reliability. The device has an interposer chip. First internal electrodes connected to core chips are formed on the first surface of the interposer chip. Second internal electrodes connected to an interface chip and third internal electrodes connected to external electrodes are formed on the second surface of the interposer chip. The interface chip can be mounted on the second surface of the interposer chip whenever desired. Therefore, the memory device can have any specification desirable to a customer, only if an appropriate interface chip is mounted on the interposer chip, as is demanded by the customer. Thus, the core chips do not need to be stocked in great quantities in the form of bare chips.