Self-aligned trench MOSFET structure and method of manufacture

A method of forming a trench gate field effect transistor (FET) in a semiconductor die comprising an active region wherein active transistor cells are formed and a termination region surrounding the active region, the method comprising:

• forming a well region in the active region and the termination region at the same time, the well region being formed in a silicon region having a conductivity type opposite that of the well region;
• simultaneously forming a plurality of active gate trenches in the active region, a non-active gate runner trench, and a non-active termination trench in the termination region, the plurality of active gate trenches, the non-active gate runner trench, and the non-active termination trench extending into and penetrating through the well region to thereby divide the well region into a plurality of active body regions in the active region and a termination body region in the termination region;
• forming a recessed active gate electrode in each active gate trench and a recessed gate runner electrode in the non-active gate runner trench at the same time, the recessed active gate electrodes being electrically connected to the recessed gate runner electrode;
• defining an opening over the termination body region and an opening over the active region using a mask;
• implanting dopants into the active body regions through the opening in the active region and into the termination body region through the opening over the termination body region, thereby forming a first region in each active body region and in the termination body region, the first regions having a conductivity type opposite that of the well region;
• and
• recessing exposed surfaces of all first regions using a silicon etch to form a bowl-shaped silicon recess having slanted walls and a bottom protruding through the first region such that portions of each first region remain in a corresponding active body region, the remaining portions of the first region in the active body regions forming source regions which are self-aligned to the active gate trenches.