An object of the invention is to provide a semiconductor device and an adjusting method for a semiconductor device wherein power source noises and noises radiated as radio waves can be reduced and power source noises inside the semiconductor device can be cut. The open stub OS1 is formed in the upper wiring layer of the semiconductor device 1. The stub length L1 is set to a length of ¼ of the wavelength of the known frequency containing peak components of noises. The noise receiving part AT1 is disposed adjacent to the open stub OS1. The open stub OS1 is connected to the power source wiring 4 by an interlayer wiring 6. The noise receiving part AT1 is biased to a ground potential. The basic wave component and odd-number harmonic waves of noises that are generated from the PLL circuit 11 and propagate (the arrow Y1 of FIG. 2) in the power source wiring 4 are reflected (arrow Y2 of FIG. 2) by the open stub OS1 so as to return to the PLL circuit 11, and do not reach the filter circuit 12.