A lateral semiconductor device formed on a semiconductor substrate having a lateral MOS transistor structure and configured to be used in a sense circuit for current detection, comprising a MOS transistor region, a diode region and a trench isolation structure separating the MOS transistor from the diode, the MOS transistor region comprising: a first conductive-type body region formed in the semiconductor substrate; a second conductive-type drain-drift region adjacent to or apart from, and laterally entirely enveloping the first conductive-type body region; a second conductive-type drain region in contact with the second conductive-type drain-drift region; a second conductive-type source region formed in the body region; an insulating film covering an upper side of the second conductive-type drain drift region and the body region from an end of the second conductive-type source region; and a gate electrode covering the upper side of the second conductive-type drain drift region from an upper end of the second conductive-type source region through the insulating film; the trench isolation structure including a trench isolation insulating film adjacently in contact with an end portion of the first conductive-type body region and the second conductive-type drain-drift region,respectively; the diode region including: a first conductive-type anode region adjacent to the trench isolation structure; a second conductive-type cathode region adjacent to the trench isolation structure;and the insulating film covering an upper side of the second conductive-type cathode region from an end of the first conductive-type anode region; wherein the first conductive-type body region and anode region each have the same impurity profile and the same region width at least at a region adjacent to the trench isolation structure, the second conductive-type drain drift region and cathode region each have the same impurity profile and the same region width at least at a region adjacent to the trench isolation structure, and wherein the first conductive-type anode region is electrically coupled to the body region through a wiring layer, the second conductive-type cathode region is electrically coupled to the second conductive-type drain region through a wiring layer, and the gate electrode is electrically coupled to a diode field plate electrode formed on said insulating film and extending from an upper side of the first conductive-type anode region to the upper side of the second conductive-type cathode region. a first conductive-type body region formed in the semiconductor substrate; a second conductive-type drain-drift region adjacent to or apart from, and laterally entirely enveloping the first conductive-type body region; a second conductive-type drain region in contact with the second conductive-type drain-drift region; a second conductive-type source region formed in the body region; an insulating film covering an upper side of the second conductive-type drain drift region and the body region from an end of the second conductive-type source region; and a gate electrode covering the upper side of the second conductive-type drain drift region from an upper end of the second conductive-type source region through the insulating film; the trench isolation structure including a trench isolation insulating film adjacently in contact with an end portion of the first conductive-type body region and the second conductive-type drain-drift region,respectively; the diode region including: a first conductive-type anode region adjacent to the trench isolation structure; a second conductive-type cathode region adjacent to the trench isolation structure;and the insulating film covering an upper side of the second conductive-type cathode region from an end of the first conductive-type anode region; wherein the first conductive-type body region and anode region each have the same impurity profile and the same region width at least at a region adjacent to the trench isolation structure, a first conductive-type anode region adjacent to the trench isolation structure; a second conductive-type cathode region adjacent to the trench isolation structure;and the insulating film covering an upper side of the second conductive-type cathode region from an end of the first conductive-type anode region; wherein the first conductive-type body region and anode region each have the same impurity profile and the same region width at least at a region adjacent to the trench isolation structure, the second conductive-type drain drift region and cathode region each have the same impurity profile and the same region width at least at a region adjacent to the trench isolation structure, and wherein the first conductive-type anode region is electrically coupled to the body region through a wiring layer, the second conductive-type cathode region is electrically coupled to the second conductive-type drain region through a wiring layer, and the gate electrode is electrically coupled to a diode field plate electrode formed on said insulating film and extending from an upper side of the first conductive-type anode region to the upper side of the second conductive-type cathode region.