A semiconductor device of the generation with the minimum processing dimensions of 90 nm, or later, wherein variation of processing dimensions of gate electrodes in a logic block and a power source noise are suppressed; wherein a gate electrode formed to have a comb-shaped pattern is formed on a normal cell region, a dummy gate electrode formed to have a comb-shaped pattern is formed on a vacant region, a wiring for applying a predetermined voltage is connected respectively to at least a part of the dummy gate and the semiconductor substrate (source drain regions), and an electrostatic capacity between the part of the dummy gate electrode and the semiconductor substrate constitutes a decoupling capacitor of the power source.