| 摘要 |
There is disclosed an IGBT which includes an n+ layer (2A), an n- layer (2B), a p well region (3), an n+ diffusion region (4), a gate oxide film (5), a gate electrode (6) and an emitter electrode (8) around the upper major surface of a p+ substrate (1), similarly to conventional IGBTs. In the lower major surface of the p+ substrate (1) is formed an n+ diffusion region (10) which adapted not to reach the n+ layer (2A). The n+ diffusion region (10) and p+ substrate (1) are connected to a collector electrode (9). When there is a small potential difference between the emitter and collector electrodes, holes are injected from the p+ substrate into the n- layer to provide a low ON-resistance. When the potential difference is large, a depletion layer extending from the n+ diffusion region is brought into a reach-through state to limit an increase in the amount of injected holes. This prevents the device from being broken down due to an excessively increased current density.
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