A discrete semiconductor device has a substrate with a first conductivity type of semiconductor material. A first semiconductor layer is formed over the substrate. The first semiconductor layer having the first conductivity type of semiconductor material. A second semiconductor layer over the first semiconductor layer. The second semiconductor layer has a second conductivity type of semiconductor material. A trench is formed through the second semiconductor layer and extends into the second semiconductor layer. The trench has a rounded or polygonal shape and vertical sidewalls. The trench is lined with an insulating layer and filled with an insulating material. A boundary between the first and second semiconductor layers forms a p-n junction. The trench surrounds the p-n junction to terminate the electric field of a voltage imposed on the second semiconductor layer. The discrete semiconductor device can also be a transistor, thyristor, triac, or transient voltage suppressor.