METHOD OF FORMING AN MOS TRANSISTOR AND STRUCTURE THEREFOR

摘要

A method for forming a MOS transistor is provided to obtain a high reverse breakdown voltage while having a low gate-to-source/drain capacitance and a low on-resistance by forming a second insulator thicker than a first insulator. A body region of a MOS transistor is formed as a first doping region(42) of a second conductivity type in a substrate(40) of a first conductivity type, electrically coupled to a conductor(36). An opening having a sidewall extends to the substrate and the first doping region. A gate structure of the MOS transistor is formed in the opening, including first and second insulators. The first insulator has a first thickness along a first portion of the sidewall. The second insulator has a second thickness greater than a first thickness along another portion of the sidewall. The first doping region can be covered with a second doping region of the first conductivity type. The first insulator can be disposed in parallel with a part of the first doping region. The second insulator is disposed in parallel with a part of the second doping region.