Abstract: To ensure bulk breakdown when the mesa diode with a positive bevel angle is reverse biased, the diffused region is formed with thinner edge portions. This eliminates corner or edge effects which create conditions of high electric field, resulting in decreased breakdown voltage and clamping voltage levels. The edges of the surface of epitaxial region are covered with a narrow oxide layer prior to diffusion. The middle portion of the surface remains uncovered. Diffusing through the oxide results in a diffused region which is thinner along the edges of the device than in the interior region below the exposed surface portion. The oxide thickness controls the depth of the edge diffusion.