Integrated semiconductor circuit having improved breakdown voltage characteristics

摘要

It is possible to limit the voltage across a diode to the level of the pinch-off voltage of a JFET in an integrated circuit by connecting the diode in series with the JFET. As a result, the voltage offered through the JFET can be higher than the breakdown voltage of the diode, which is of particular importance in high-voltage ICs in which a highly doped buried zone is formed below the diode for reducing leakage currents to the substrate. According to the invention, the JFET together with at least one further circuit element is formed in a common island surrounded by an island insulation region. The gate of the JFET extends along the edge of the island and is separated from the relevant portion of the island insulation region substantially only by the source of the JFET. In the pinch-off condition, the gate divides the island into a high-voltage portion and a low-voltage portion which is coupled to the diode. The diode with the JFET occupies very little space and can be readily incorporated in integrated circuit designs.