A method and structure suitable for, e.g., improving high voltage breakdown reliability of a microelectronic device such as a capacitor usable for galvanic isolation of two circuits. A first dielectric layer has a first dielectric constant located over a semiconductor substrate. A metal structure located over the first dielectric layer has a side surface. A second dielectric layer having a second different dielectric constant is located adjacent the metal structure. A dielectric structure located between the side surface of the metal structure and the second dielectric layer has the first dielectric constant.