An integrated circuit (IC) (20) is formed on a semiconductor substrate (21). The IC has a PN junction (28) and a graded junction termination (27). A reverse field plate (31) is mounted adjacent the junction termination. One end of the field plate is mounted on and electrically connected to the substrate; the remainder of the field plate extends over a passivating oxide layer (30) which covers the substrate surface (29) adjacent the junction termination. The field plate provides a common potential surface which maintains a fixed potential on the substrate surface at the junction termination.