A semiconductor device includes an insulating substrate including a first surface and an opposing second surface, and a semiconductor chip. The semiconductor chip is mounted over the first surface, includes signal electrodes, power-supply electrodes and ground electrodes, which connect to pads on the first surface of the insulating substrate. Lands provided on the second surface of the insulating substrate include signal lands, power-supply lands and ground lands through vias penetrate from the first surface to the second surface of the insulating substrate, and include signal vias electrically connected the signal connection pads to the signal lands, power-supply vias electrically connected the power-supply connection pads to the power-supply lands and ground vias electrically connected the ground connection pads to the ground lands. At least one of the signal vias are closer to the connection pads than immediately adjacent one of the power-supply vias or the ground vias.