| 摘要 |
A trench MOSFET is formed in a structure which includes a P-type epitaxial layer overlying an N+ substrate. A trench is formed in the epitaxial layer. A deep implanted N layer is formed below the trench at the interface between the substrate and the epitaxial layer, and N-type dopant is implant through the bottom of the trench to form an N region in the epitaxial layer below the trench but above and separated from the deep N layer. The structure is heated to cause the N layer to diffuse upward and the N region to diffuse downward. The diffusions merge to form a continuous N-type drain-drift region extending from the bottom of the trench to the substrate. Alternatively, the drain-drift region may be formed by implanting N-type dopant through the bottom of the trench at different energies, creating a stack of N-type regions that extend from the bottom of the trench to the substrate. |
