US Patent 7411248 Vertical unipolar component periphery

A vertical unipolar component formed in a semiconductor substrate, comprising vertical fingers made of a conductive material surrounded with silicon oxide, portions of the substrate being present between the fingers and the assembly being coated with a conductive layer. The component periphery includes a succession of fingers arranged in concentric trenches, separated from one another by silicon oxide only, the upper surface of the fingers of at least the innermost rank being in contact with said conductive layer.