<p>In order to detect whether a leak current is generated by gate destruction in a transistor (Qds) which receives boost voltage of a boost circuit (40), a semiconductor device includes: a constant current circuit (46) which receives an external power source voltage and supplies a constant current to a boost voltage output node (BN_1) of the boost circuit while the the boost operation of the boost circuit is in a stop state; and a comparison circuit (47) which performs a comparison between the boost voltage output node voltage varied by the power supply from the constant current circuit and a reference voltage (Vref). When the comparison circuit decides that the boost voltage output node voltage is a predetermined voltage lower than the power source voltage, it is possible to judge that the leak current is generated. Thus, it is possible to effectively detect a leak current generated by destruction of a transistor which receives a high voltage.</p>
