A semiconductor device, comprising: a wiring substrate including: a lower substrate selected from the group consisting of a silicon substrate, a glass substrate, or a substrate in which a silicon substrate and a glass substrate are joined; through electrodes formed in the lower substrate, and penetrating from an upper surface to a lower surface of the lower substrate; a cooling passage for carrying water, formed in the lower substrate and penetrating from a side surface of one end of the lower substrate to a side surface of the other end side of the lower substrate; means for causing water to flow in a preset direction through the cooling passage when the semiconductor device is in use; a built-up wiring formed on one side of the lower substrate and connected to the through electrodes; and a plurality of semiconductor chips (68a, 68b, 69a, 69b) mounted on the wiring substrate and connected to the built-up wiring, including a lower semiconductor chip (69a, 69b) mounted on the other side of the lower substrate and connected to the built-up wiring via a through electrode, wherein at least one of the semiconductor chips generates a smaller amount of heat than another one of the semiconductor chips when the device is in use; wherein the plurality of semiconductor chips (68a, 68b, 69a, 69b) on the wiring substrate are arranged along the cooling passage such that the said one semiconductor chip is arranged on an inflow side of the cooling passage and the said other semiconductor chip is arranged on an outflow side of the cooling passage, relative to one another. a wiring substrate including: a lower substrate selected from the group consisting of a silicon substrate, a glass substrate, or a substrate in which a silicon substrate and a glass substrate are joined; through electrodes formed in the lower substrate, and penetrating from an upper surface to a lower surface of the lower substrate; a cooling passage for carrying water, formed in the lower substrate and penetrating from a side surface of one end of the lower substrate to a side surface of the other end side of the lower substrate; means for causing water to flow in a preset direction through the cooling passage when the semiconductor device is in use; a built-up wiring formed on one side of the lower substrate and connected to the through electrodes; and a plurality of semiconductor chips (68a, 68b, 69a, 69b) mounted on the wiring substrate and connected to the built-up wiring, including a lower semiconductor chip (69a, 69b) mounted on the other side of the lower substrate and connected to the built-up wiring via a through electrode, wherein at least one of the semiconductor chips generates a smaller amount of heat than another one of the semiconductor chips when the device is in use; wherein the plurality of semiconductor chips (68a, 68b, 69a, 69b) on the wiring substrate are arranged along the cooling passage such that the said one semiconductor chip is arranged on an inflow side of the cooling passage and the said other semiconductor chip is arranged on an outflow side of the cooling passage, relative to one another. a lower substrate selected from the group consisting of a silicon substrate, a glass substrate, or a substrate in which a silicon substrate and a glass substrate are joined; through electrodes formed in the lower substrate, and penetrating from an upper surface to a lower surface of the lower substrate; a cooling passage for carrying water, formed in the lower substrate and penetrating from a side surface of one end of the lower substrate to a side surface of the other end side of the lower substrate; means for causing water to flow in a preset direction through the cooling passage when the semiconductor device is in use; a built-up wiring formed on one side of the lower substrate and connected to the through electrodes; and a plurality of semiconductor chips (68a, 68b, 69a, 69b) mounted on the wiring substrate and connected to the built-up wiring, including a lower semiconductor chip (69a, 69b) mounted on the other side of the lower substrate and connected to the built-up wiring via a through electrode, wherein at least one of the semiconductor chips generates a smaller amount of heat than another one of the semiconductor chips when the device is in use; wherein the plurality of semiconductor chips (68a, 68b, 69a, 69b) on the wiring substrate are arranged along the cooling passage such that the said one semiconductor chip is arranged on an inflow side of the cooling passage and the said other semiconductor chip is arranged on an outflow side of the cooling passage, relative to one another.