A semiconductor IC device is designed using a memory core with a plurality of I/O lines, a transfer circuit module and a logic library which are produced beforehand and stored in a data base. The memory core and a logic circuit are arranged so that their I/O lines extend in the same direction. A transfer circuit including plural stages of switch groups is arranged between the I/O lines of the memory core and the I/O lines of the logic circuit. Switches forming each stage of switch group are formed between the I/O lines of the memory core and the I/O lines of the logic circuit. When one stage of or a small number of stages of switch groups are turned on, the I/O lines of the memory core and the I/O lines of the logic circuit are turned on, thereby forming a desired transfer pattern. The memory core is constructed by the combination of functional modules such as an amplifier module, a bank module and a power supply module. In the bank module are arranged row-system circuits which operate independently of each other and a multiplicity of I/O lines which extend in a bit line direction.