| 摘要 |
Proton implantation is performed a plurality of times to form a plurality of n-type buffer layers (5, 6, 7) in an n-type drift layer (2) at different depths from a rear surface of a substrate. The depth of the n-type buffer layer (5), which is provided at the deepest position from the rear surface of the substrate, from the rear surface of the substrate is more than 15 µm. The temperature of a heat treatment which is performed in order to change a proton into a donor and to recover a crystal defect after the proton implantation is equal to or higher than 400°C. In a carrier concentration distribution of the n-type buffer layer (5), a width from the peak position (5a) of carrier concentration to an anode is more than a width from the peak position (5a) to a cathode. The carrier concentration of regions (15, 16) interposed between the n-type buffer layers (5, 6, 7) is flat and is equal to or more than the carrier concentration of an n-type silicon substrate (1) and equal to or less than five times the carrier concentration of the n-type silicon substrate (1). Therefore, it is possible to ensure a breakdown voltage and to reduce generation loss. It is possible to suppress the oscillation of voltage and current during a switching operation. In addition, it is possible to recover the crystal defect and to reduce a leakage current. Accordingly, it is possible to reduce the risk of thermal runaway. |
