In a storage system directly connected to a network, if conventional interfaces and protocols are used when an IO command issued from a file server is transmitted to the storage system, the commanddata is serially transferred via a single transfer path so that the performance is lowered. The fastener includes a first member having a cavity and a second member sized to be rotatably attached within the cavity. Second stressed regions having a second type of stress underlie the source and drain regions, in which the second type of stress is an opposite one of the compressive type or tensile type stress of the first stressed region.