A semiconductor device having a first semiconductor chip with an SDRAM and a second semiconductor chip with a an MPU controlling the SDRAM. The contour size of the semiconductor device is reduced to a smaller size without impairing the testability of the first semiconductor chip. The two semiconductor chips are stacked over the top surface of an interconnect substrate and sealed in a molding resin, thus forming an SiP (System-in-Package). First terminals electrically connected with the second chip are arranged as external terminals of the SiP on the outer periphery of the bottom surface of the interconnect substrate. Plural second electrodes electrically connected with interconnects, which electrically connect the two chips, are mounted as terminals for testing of the SDRAM. The second electrodes are located more inwardly than the innermost row of the first external electrodes on the bottom surface of the interconnect substrate.