| 摘要 |
An insulated gate field effect transistor comprising a semiconductor substrate having one side on which a cell area is composed of a plurality of first wells of a first conductivity type, each of the first wells containing a source region of a second conductivity type, a channel region is defined in the surface portion of the semiconductor substrate adjoining to the source region, a gate electrode is formed, via a gate insulating film, at least over the channel region, a source electrode is in common contact with the respective source regions of the plurality of first wells; the semiconductor substrate having the other side on which a drain electrode is provided; and a current flowing between the source electrode and the drain electrode through the channel being controlled by a voltage applied to the gate electrode; wherein: a guard ring area is disposed on the one side of the semiconductor substrate so as to surround the cell area; and the source electrode has an extension connected to a second well of a second conductivity type formed in the one side between the cell area and the guard ring area to provide a by-pass such that, when a current concentration occurs within the guard ring area, the concentrated current is conducted directly to the source electrode in the cell area through the by-pass, thereby preventing the concentrated current from causing a forward biassing between the first wells and the source region. <IMAGE> |
