Disclosed are MOSFET devices in which a region extends from the drain and is, self-aligned with the gate. The region has a lower dopant concentration than the drain. The presence of the extension region substantially enhances breakdown voltage while not adding excessive on-resistance...http://www.google.com/patents/US5846866?utm_source=gb-gplus-sharePatent US5846866 - Drain extension regions in low voltage lateral DMOS devices
