Patent ID: 8604560

Claim:
A transistor power switch device comprising: a semiconductor body presenting opposite first and second faces; an array of vertical field-effect transistor elements for carrying current between said first and second faces, wherein said array of transistor elements comprises at said first face an array of source regions of a first semiconductor type, at least one body region of a second semiconductor type opposite to said first type interposed between said source regions and said second face, at least one drain region of said first semiconductor type electrically connected with said second face, and at least one control electrode for switchably controlling flow of said current through said at least one body region, and a conductive layer contacting said source regions and insulated from said control electrode by at least one insulating layer; and wherein said source region of each of said vertical transistor elements contacting said conductive layer comprises a plurality of arms extending radially at said first face towards an arm of a source region of an adjacent vertical transistor element of said array, said at least one body region extending around and under said arms of said source regions and merging between said vertical transistor elements to form a continuous body region, and said at least one body region extending up within each of said source regions to contact said conductive layer at said first face at a contact position at an outer end of each of said arms of said source regions.