| 摘要 |
An IGBT chip includes a unit cell region and a guard ring region which surrounds the unit cell region. In the unit cell region, a plurality of IGBT unit cells are formed, each of which comprises a base layer, a source layer, a common gate electrode, a common source electrode, and a common drain electrode. In the guard ring region, at least one diffused layer making up a guard ring is formed. Further, an annular diffused layer is formed and is connected to the drain electrode. The annular diffused layer is disposed away from the outermost guard ring by a specified length. This length is such that the punch-through occurs before the avalanche breakdown voltage of the junction associated with the outermost guard ring. Therefore, the withstand voltage against the avalanche breakdown when surge voltage is applied to the drain electrode is improved.
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