Abstract: A packaged semiconductor device that enables testing of semiconductor chips incorporated therein in a simplified and efficient manner. The semiconductor device includes a packaged logic chip for processing data and a packaged memory chip for storing data that is processed by or that is to be processed by the logic circuit. The semiconductor device has an automatic rewrite circuit and a selector. The automatic rewrite circuit automatically writes test data to the memory circuit in accordance with a command signal from a tester. The selector selectively switches between accessing of the memory circuit by the automatic rewrite circuit and accessing of the memory circuit by the logic circuit. The tester provides the automatic rewrite circuit with a test start command signal to start testing the logic circuit.