A semiconductor device includes a power element and a heat sensing element configured to detect a temperature of the power element. The power element includes lateral MOS transistors having drains and gate electrodes, two of the drains being shorter in length than the remaining drains and two of the gate electrodes being shorter in length than the remaining gate electrodes. The heat sensing element has a rectangular shape and is disposed between the two shorter drains and the two shorter gate electrodes to accurately detect the temperature of the power element.