Methods of forming a power semiconductor device having an edge termination are provided in which the power semiconductor device that has a drift region of a first conductivity type is formed on a substrate. An ultrasonic waveguide in the internal chamber ultrasonically energizes liquid within the chamber prior to the liquid being exhausted through the exhaust port. The model creation part creates a foreground model of the foreground area and a background model of the background area which are modified, based on first pixel values of a predetermined line segment where the modification is instructed and second pixel values of the foreground area and the background area which are divided. Each flap defines only a portion of the circumference.