Disclosed herein is a method for designing a semiconductor device, the method including: assigning a plurality of wiring tracks including first and second tracks; connecting a first data I/O circuit to a first data node of a first circuit by a first signal bus arranged on the first wiring track; connecting a second data I/O circuit to a second data node of the first circuit by a second signal bus arranged on the second wiring track when a first design mode is selected; and connecting the first data I/O circuit to a second circuit by a second signal bus arranged on the second wiring track when a second design mode is selected.