Abstract: A semiconductor device includes a semiconductor body (1, 2) with an island-shaped region (3) adjoining the surface, in which a contact pad (6) is provided above the island-shaped region (3) and separated therefrom by an insulating layer (5). The island-shaped region (3) forms a pn-junction (34) with an adjoining isolating region (4). According to the invention, the device is provided with regions (40, 41) for increasing the breakdown voltage of the pn-junction (34).

Abstract: P-type isolation regions, which surround an island of an n-type epitaxial layer, are formed by providing a p-type dopant at a part of the surface of a p-type silicon substrate. After growing the layer a p-type dopant is also provided at the surface of the layer opposite the part of the substrate surface where the dopant is provided. The dopants are diffused into the layer until the p-type regions meet. To inhibit diffusion of the p-type dopant during epitaxial growth, an n-type dopant having a lower diffusion coefficient than that of the p-type dopant is provided at the part of the substrate surface before providing the epitaxial layer. Formation of the isolation regions can be carried out simultaneously with the formation of p-type regions of a circuit element, for example a transistor, in the islands.