The invention provides a low cost and high performance functional circuit by reducing time required for the repetition of logic synthesis and routing of layout in a functional circuit design. A standard cell used for the logic synthesis and the routing of layout is configured by a logic circuit on an output side and a logic circuit on an input side and a driving capacity of the logic circuit on the output side is made large while gate input capacitance of the logic circuit on the input side is made small. By forming the standard cell in this manner, a ratio that the gate delay occupies in the delay time of a functional circuit can be relatively increased. Therefore, even when wiring capacitance after the routing of layout is not estimated at high precision in advance, an operating frequency can be obtained at high precision in the logic synthesis as long as a gate delay of each standard cell can be estimated at high precision. That is, a reliability of the logic synthesis result is improved, therefore, the logic synthesis and an automatic routing of layout are not required to be repeated, which can shorten the design period.