Termination structure for trench DMOS device and method of making the same

A trench DMOS device and a termination structure provided therefor, comprising:

• a substrate of a first type conductivity;
• an epitaxial layer of said first type conductivity over said substrate, said epitaxial layer having a lower doping concentration than said substrate;
• a body region of a second type conductivity within said epitaxial layer;
• a plurality of first type trenches through said body region in an active area of said substrate;
• a second type trench through said body region between said active area and an edge of said substrate, said second type trench having a greater width than said first type trenches;
• a plurality of contact holes in said body region between said first type trenches;
• a plurality of contact regions of said second type conductivity within exposed portions of said body region in said first type trenches;
• a plurality of doped regions of said first type conductivity within said body region sandwiched between said contact holes and said first type trenches;
• a gate oxide layer lining said first type trenches and said second type trench and extending to upper surfaces of said doped regions in said active area and said body region between said active area and said edge of said substrate;
• a plurality of gate electrodes filling said first type trenches;
• a passivation layer covering said gate oxide layer and said gate electrodes;
• a metal layer provided on said passivation layer and filling said contact holes and said second type trench;
• and
• an opening in said metal layer to expose a part of said passivation layer over a bottom surface of said second type trench, portions of said passivation layer on side walls of said second type trench being covered by said metal layer.

A trench DMOS device, comprising:

• a semiconductor substrate having a trench DMOS active area formed on said substrate and spaced from an edge of said substrate;
• a termination area trench disposed between said active area and said edge of said substrate, said termination area trench having a depth extending partially into said substrate, said termination area trench having a bottom surface and side walls disposed between a pair of upper surfaces;
• a passivation layer covering said bottom surface and side walls of said termination area trench and said pair of upper surface;
• and
• a metal layer covering portions of said passivation layer on the side walls of said termination area trench to expose a part of said passivation layer over the bottom surface of said termination area trench.