PROBLEM TO BE SOLVED: To provide a semiconductor device with its size reduced and with its manufacturing method simplified.;SOLUTION: The semiconductor device has a heterojunction semiconductor region 9 forming a heterojunction with a drain region 2, is connected to a source electrode 7, and is different in band gap from the semiconductor substrate that constitutes the drain region 2. By changing the conductivity type or the impurity concentration level of the heterojunction semiconductor region 9, the magnitude of the energy barrier it forms with the drain region 2 for electrons in conduction can be set as required. This is an attribute not shared with the Schottky junction wherein the magnitude of the energy barrier is principally determined by the work function of the metal material. An optimum design is easily drawn for a passive element corresponding to the voltage resistance system of a MOSFET working as the switching element, and the diffusion potential is suppressed in case of reverse direction conduction for an integration improvement per unit area. In this way, the element size is reduced, and the manufacturing process is simplified.;COPYRIGHT: (C)2005,JPO&NCIPI
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