CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2020-043815, filed on Mar. 13, 2020; the entire contents of which are incorporated herein by reference.

FIELD

Embodiments relate to a semiconductor device.

BACKGROUND

It is desirable for a semiconductor device for power control to have characteristics of a low on-resistance and a small switching loss. For example, in an IGBT (Insulated gate Bipolar Transistor), the on-resistance can be reduced by increasing the density of holes injected from a p-type collector layer into an n-type base layer. However, as the hole density increases in the n-type base layer, it takes long time to eject the holes from the n-type base layer, resulting in an increase of the turn-off loss.

The IGBT comprising two control electrodes that are controlled independently is used to improve such a trade-off relation and reduce both the on-resistance and the turn-off loss. For example, the holes are partly pre-ejected from the n-type base layer by controlling the potential of one of the two control electrodes before turning off the IGBT, thus, reducing the hole density in the n-type base layer. Thereby, the ejection time of holes can be shortened while turning off the IGBT, and the switching loss can be reduced. However, some constraints must be eliminated in a circuit design to achieve such a gate control.

