In an electro processor for plating semiconductor wafers and similar substrates, a contact ring has a plurality of spaced apart contact fingers. A shield at least partially overlies the contact fingers. The shield changes the electric field around the outer edge of the workpiece and the contact fingers, which reduces or eliminates the negative aspects of using high thief electrode currents and seed layer deplating. The shield may be provided in the form of an annular ring substantially completely overlying and covering, and optionally touching the contact fingers.