An overvoltage protection devices operable to provide protection against overvoltage events of positive and negative polarity, comprising: an N P N semiconductor structure defining: a first N-type region; a first P-type region; and a second N-type region; wherein one of the first or second N-type regions is connected to a terminal, conductor or node that is to be protected against an overvoltage event, and the other one of the first or second N-type regions is connected to a reference, and wherein a field plate is in electrical contact with the first P-type region, and the field plate overlaps with but is isolated from portions of the first and second N type regions.