LDMOS transistor with reduced projective area of source region

A semiconductor device comprising:

• (a) a semiconductor substrate of a first conductivity type;
• an insulating material disposed over said substrate to define an active region, a first predetermined location of said active region implanted with impurities of the first conductivity type to form a drain region;
• (c) a gate electrode disposed at a second predetermined location of the active region;
• (d) a trench therein adjacent said gate electrode, said trench having:
• (i) first sidewalls which intersect said substrate essentially normal to a major surface thereof and extend in a direction normal to said major surface for a predetermined distance, and
• (ii) second sidewalls then converging towards each other as the depth of the trench in said substrate increases;
• (e) a first residual region of the substrate, said first residual region being implanted with impurities of the first conductivity type and being disposed immediately adjacent one of the first sidewalls, below and under said gate electrode, without being immediately adjacent said second sidewalls, said first residual region forming a source region;
• and
• (f) a body region implanted with impurities of a second conductivity type material surrounding said trench and said source region.