A semiconductor device is provided, which comprises a first semiconductor package, a second semiconductor package, and a connection structure. The first semiconductor package includes a first substrate. The first substrate includes a first region and a second region. The second semiconductor package is mounted on the first semiconductor package. The connection structure electrically connects the second semiconductor package and the first semiconductor package. The connection structure comprises first connection patterns at the first region. The first connection patterns provide a data signal at the first region. The connection structure further comprises second connection patterns at the second region. The second connection patterns provide a control/address signal at the second region. A number of the second connection patterns is less than a number of the first connection patterns.