A novel LDMOS structure with a step gate oxide

High performance power device is essential for power integrated circuits and discrete power devices. A novel LDMOS structure with step gate oxide is proposed for breakdown voltage or on state resistance (Ron) improvement. The step gate oxide is introduced on the LDMOS's drift region. The thicker step gate oxide can improve device breakdown voltage without significantly affecting other device electric parameters. As a result, drain can be pulled back and self-aligned to the gate. This can significantly reduce device drift region and improves device on state resistance. This approach is different from conventional approach (with or without field oxide on the drain side) which drain is not self-aligned to the gate.