Field effect transistor and manufacturing method thereof.

摘要

A field effect transistor comprises a spreading layer (12) between an n<+> type substrate (21) and an n<-> type epitaxial layer (22). The mean specific resistance of the spreading layer (12) in such a field effect transistor is relatively low, so that the total amount of the ON resistance of the device can be considerably decreased compared with conventional structures. Further, the breakdown voltage of the device can be maintained at a high value by virtue of a gentle impurity concentration distribution in the spreading layer (12).