Abstract: In an IGBT with a current sensing function having a plurality of principal current cells and at least one current sensing cell, a P-type base region of the current sensing cell in a current sensing cell region is formed larger than a P-type base region of the principal current cell in a principal current cell region. The IGBT is so constituted that the influence of temperature characteristic of parasitic resistor between the principal current cells and current sensing cell upon detected current can be eliminated and the same interval between the P-type base regions can be set for all the cells.

Abstract: In a semiconductor device comprising a semiconductor chip on which semiconductor elements are formed, the semiconductor device further comprises a thermal resistance detector for detecting an increase of thermal resistance of a heat radiating path which is provided to radiate the heat generated in the semiconductor device during operation, and a thermal resistance detection result output circuit for outputting a result of a detection by the thermal resistance detector to an output of the semiconductor device. The semiconductor device can detect at the early stage the increase of the thermal resistance of the heat radiating path, and the deterioration of the semiconductor device due to the crack in the solder layer bonding the chip mounting insulation substrate and heat sink during the operation of the device.