Method of forming trench gate field effect transistor with recessed mesas
A monolithically integrated field effect transistor and Schottky diode includes gate trenches extending into a semiconductor region. Source regions having a substantially triangular shape flank each side of the gate trenches. A contact opening extends into the semiconductor region between adjacent gate trenches. A conductor layer fills the contact opening to electrically contact: (a) the source regions along at least a portion of a slanted sidewall of each source region, and (b) the semiconductor region along a bottom portion of the contact opening, wherein the conductor layer forms a Schottky contact with the semiconductor region.
1. A method of forming a field effect transistor comprising an active area and a termination region surrounding the active area, the method comprising:
forming gate trenches extending into a silicon region of a first conductivity type;
forming a well region of a second conductivity type in the silicon region;
forming a recessed gate in each gate trench;
forming a dielectric cap over each gate;
recessing all exposed surfaces of the well region to form a recess in the well region between every two adjacent trenches such that the recess has sloped walls and a bottom located between a top surface of the dielectric cap and a top surface of the recessed gate; and
without masking any portion of the active area, performing a zero-degree blanket implant to form a heavy body region of the second conductivity type in the well region between every two adjacent trenches whereby the heavy body region is self-aligned to the gate trenches.
2. The method of claim 1 further comprising performing a two-pass angled implant into the sloped walls of each recess to thereby form source regions of the first conductivity type adjacent the dielectric cap, the sloped walls of the recess forming an outer wall of each source region, the source regions being self-aligned to the trenches.
3. The method of claim 2 further comprising forming a source conductor contacting the outer wall of each source region and contacting the heavy body region along the bottom of the recess.
4. The method of claim 1 further comprising:
forming a wide trench in the termination region; and
filling the wide trench with LOCOS.
5. The method of claim 1 further comprising forming a surface gate in the termination region simultaneously with forming the recessed gate in the gate trenches.
6. The method of claim 5 further comprising:
forming an opening over the surface gate; and
forming a gate conductor contacting the surface gate through the opening.
7. The method of claim 1 further comprising:
forming a termination trench in the termination region simultaneously with forming the gate trenches;
forming a recessed gate in the termination trench simultaneously with forming the recessed gate in the gate trenches;
forming an opening over the recessed gate in the termination trench; and
forming a gate conductor contacting the recessed gate in the termination trench through the opening.
8. The method of claim 5 further comprising:
forming an opening over the surface gate; and
simultaneously with recessing all exposed surfaces of the well region, recessing the surface gate through the opening to thereby expose sidewalls of the surface gate through the opening; and
filling the opening with a gate conductor, the gate conductor contacting the surface gate along the exposed sidewalls of the surface gate.
9. The method of claim 1 further comprising:
simultaneously with forming the gate trenches, forming a wide trench in the termination region; and
filling a bottom portion of the wide trench and each gate trench with LOCOS.
10. The method of claim 9 further comprising forming a termination gate simultaneously with forming the recessed gate in the gate trenches, the termination gate extending in part inside the wide trench and in part over a mesa region adjacent the wide trench.
11. The method of claim 10 further comprising:
forming a contact opening over the termination gate in the wide trench; and
simultaneously with recessing all exposed surfaces of the well region, recessing the termination gate through the opening to thereby expose sidewalls of the termination gate through the opening; and
filling the opening with a gate conductor, the gate conductor contacting the exposed sidewalls of the termination gate.
12. The method of claim 1 further comprising:
prior to forming the recessed gate, forming a thick bottom dielectric along a bottom portion of each gate trench; and
prior to forming the recessed gate, forming a gate dielectric lining the sidewalls of each gate trench, wherein the thick bottom dielectric is thicker than the gate dielectric.
13. The method of claim 1 further comprising:
prior to forming the recessed gate, forming a shield electrode along a bottom portion of each gate trench; and
prior to forming the recessed gate, forming a dielectric layer over each shield electrode.