A technique which reduces the influence of external noise such as crosstalk noise in a semiconductor device to prevent a circuit from malfunctioning. A true signal wire and a bar signal wire which are susceptible to noise and part of an input signal line to a level shifter circuit, and shield wires for shielding these signal wires are laid on an I/O cell. Such I/O cells are placed side by side to complete a true signal wire connection and a bar signal wire connection. These wires are arranged in a way to pass over a plurality of I/O cells and are parallel to each other or multilayered.