A method is provided for forming a power semiconductor device. The method
begins by providing a substrate of a first conductivity type and forming
a voltage sustaining region on the substrate. The voltage sustaining
region is formed in the following manner. First, an epitaxial layer is
deposited on the substrate. The epitaxial layer has a first or a second
conductivity type. Next, at least one terraced trench is formed in the
epitaxial layer. The terraced trench has a trench bottom and a plurality
of portions that differ in width to define at least one annular ledge
therebetween. A barrier material is deposited along the walls and bottom
of the trench. A dopant of a conductivity type opposite to the
conductivity type of the epitaxial layer is implanted through the barrier
material lining the annular ledge and at the trench bottom and into
adjacent portions of the epitaxial layer to respectively form at least
one annular doped region and another doped region. The dopant is diffused
in the annular doped region and the another doped region to cause the
regions to overlap one another, whereby a continuous doped column is
formed in the epitaxial layer. A filler material is deposited in the
terraced trench to substantially fill the terraced trench. Finally, at
least one region of conductivity type opposite to the conductivity type
of the epitaxial layer is formed over the voltage sustaining region to
define a junction therebetween.