A capacitor for sensing a substrate voltage in an integrated circuit power
device may be implemented by isolating a portion or segment of the metal
layer that normally covers the heavily doped perimeter region typically
used for electric field equalization. In conjunction, one or more portions
of an isolation dielectric layer of silicon oxide are not removed from the
surface of the semiconductor substrate, as is commonly done before
depositing the metal layer. The portions of isolated silicon oxide which
are not removed become the dielectric layer of the capacitor. Moreover,
one plate of the capacitor is formed by the heavily doped perimeter region
that is electrically connected to the substrate (e.g. a drain or collector
region). The other plate is formed by the segment of metal isolated from
the remaining metal layer defined directly over the heavily doped
perimeter region.
