Insulated Gate Bipolar Transistor Structure Having Low Substrate Leakage

A method of fabricating a high voltage semiconductor transistor, comprising:

• receiving a semiconductor substrate with first and second well regions and an implanted oxygen layer;
• forming an insulating structure over and partially embedded in the first well region, the insulating structure isolated from contact with the second well region;
• forming a gate structure near the insulating structure over the first well region;
• forming a drain region in the first well region across the insulating structure from the gate structure, wherein the drain region comprises a first drain portion nearer to the insulating structure and a second drain portion farther from the insulating structure;
• and
• forming an isolation feature in the first well region, the isolation feature being in contact with the implanted oxygen layer,
• wherein the first drain portion is separated from the second drain portion by the isolation feature, and
• wherein the isolation feature and the implanted oxygen layer together surround the second well region, the insulating structure, the gate structure, a source region and the first drain portion.

A method of fabricating a high voltage semiconductor transistor, comprising:

• implanting oxygen into a lightly doped semiconductor substrate having a first type of conductivity, the oxygen being implanted below a top surface to form an implanted oxygen layer;
• forming a doped first well region over the substrate, the first well region having a second type of conductivity different from the first type of conductivity;
• forming a first doped portion of a second well region in the first well region, the first doped portion occupying a region starting from a top surface of the first well region and extending into the first well region;
• forming a second doped portion of the second well region in the first well region, the second doped portion extending laterally from the first doped portion toward a drain region, and both the first and second portions having the first type of conductivity;
• forming an insulating layer on the substrate;
• forming a gate structure on the substrate, the gate structure having a first part overlying the insulating layer, a second part overlying the first well region, and a third part overlying the first doped portion of the second well region;
• forming a source region in the first doped portion of the second well region on an opposite side of the gate structure from the insulating layer;
• forming the drain region in the first well region;
• and
• forming a deep trench isolation feature in the substrate and the first well region,
• wherein the deep trench isolation feature surrounds the second well region, a first portion of the drain region and the insulating layer, and contacts the implanted oxygen layer.