Semiconductor device having an seb voltage suitable for use in space

Abstract

In a power MOSFET, on an Ndrain layeras a substrate, a second N base layerand a first Nbase layerare deposited in the order by epitaxial growth. In a surface portion of the layer, there are selectively formed a P base region, in a surface portion of which an Nsource regionis selectively formed. On a channel region in the P base region, a gate electrodeis formed with a gate insulator filmheld between. A source electrodeand a drain electrodeare formed on the Nsource regionand on the back of the substrate, respectively. The layeris made to have a thickness equal to or more than ¼ of that of the first Nbase layer, and an averaged impurity concentration between 1×10/cmand 3×10/cm. The thickness can be alternatively given as equal to or more than ½ of a difference between the thickness x shown as x(μm)=V(V)/8 and that of the layer, where Vis an SEB(Single Event Burnout) voltage of the layer. This makes positive feed back hard to occur between latch-up of a parasitic npn transistor and dynamic avalanche near the substrate to enhance the SEB voltage, allowing the MOSFET to be applied to space use.