Abstract: A semiconductor device has a substrate including a semiconductor material of a first conductivity type. A first layer including a semiconductor material of a second conductivity type is formed in the substrate with a boundary between the first layer and the semiconductor material of the first conductivity type as a p-n junction. A vertical trench is formed through the first layer by anisotropic etch and extends at least to the boundary. The vertical trench has a rounded or polygonal shape with a depth less than 40 micrometers. An insulating material is deposited in the vertical trench. An insulating layer is formed over a sidewall of the vertical trench. The shallow vertical trench filled with insulating material increases breakdown voltage and reduces manufacturing time and complexity. The semiconductor device can be a discrete diode, transistor, rectifier, transient voltage suppressor, silicon controlled rectifier, and triode.