An electronic device includes a transistor, wherein the electronic device can include a semiconductor layer having a primary surface, a channel region, a gate electrode, a source region, a conductive electrode, and an insulating layer lying between the primary surface of the semiconductor layer and the conductive electrode. The insulating layer has a first region and a second region, wherein the first region is thinner than the second region. The channel region, gate electrode, source region, or any combination thereof can lie closer to the first region than the second region. The thinner portion can allow for faster switch of the transistor, and the thicker portion can allow a relatively large voltage difference to be placed across the insulating layer. Alternative shapes for the transitions between the different regions of the insulating layer and exemplary methods to achieve such shapes are also described.