MOSFET having dual-gate cells with an integrated channel diode
A semiconductor device includes MOSFET cells having a drift region of a first conductivity type. A first and second active area trench are in the drift region. A split gate uses the active trenches as field plates or includes planar gates between the active trenches including a MOS gate electrode (MOS gate) and a diode gate electrode (diode gate). A body region of the second conductivity type in the drift region abutts the active trenches. A source of the first conductivity type in the body region includes a first source portion proximate to the MOS gate and a second source portion proximate to the diode gate. A vertical drift region uses the drift region below the body region to provide a drain. A connector shorts the diode gate to the second source portion to provide an integrated channel diode. The MOS gate is electrically isolated from the first source portion.
1. A semiconductor device, comprising:
a substrate;
a metal oxide semiconductor field effect transistor (MOSFET) cell including:
a drift region of a first conductivity type in the substrate;
active trenches formed adjacent to said drift region, said active trenches including an electrically conductive filler material surrounded by a trench dielectric liner;
a split gate comprising a MOS gate and a diode gate over said drift region and between said active trenches, said split gate using said active trenches as field plates;
a body region of a second conductivity type opposite from said first conductivity type abutting said active trenches, and the body region including a first body region proximate to said MOS gate and a second body region proximate to said diode gate;
a source region of said first conductivity type formed in said body region, the source region including a first source portion proximate to said MOS gate and a second source portion proximate to said diode gate;
a drain contact formed on a bottom side of said substrate opposing from the split gate, and
a connector connecting said diode gate to said second source portion to form a channel diode integrated to a MOSFET controlled by said MOS gate, wherein said MOS gate is electrically isolated from said first source portion.
2. The semiconductor device of claim 1 , wherein said second body region is lighter in doping by at least a factor of two (2) as compared to said first body region.
3. The semiconductor device of claim 1 , further comprising a termination trench abutting at least two vertical sides of said MOSFET cell.
4. The semiconductor device of claim 1 , wherein said connector comprises a metal.
5. The semiconductor device of claim 1 , wherein said connector comprises doped polysilicon.
6. The semiconductor device of claim 1 , wherein said substrate comprises silicon.
7. The semiconductor device of claim 1 , further comprising a first bus connecting said MOS gate of said MOSFET cell and a second bus connecting said diode gate of said MOSFET cell and to said second source portion.
8. The semiconductor device of claim 1 , wherein said MOS gate is configured as a MOS gate stripe and said diode gate is configured as a diode gate stripe, wherein said active trenches are aligned in parallel with said MOS gate stripe and said diode gate stripe.
9. The semiconductor device of claim 1 , wherein said MOS gate is configured as a MOS gate stripe and said diode gate is configured as a diode gate stripe, wherein said active trenches are aligned perpendicular to said MOS gate stripe and said diode gate stripe.
10. The semiconductor device of claim 1 , wherein said active trenches comprise active trench wells.
11. The semiconductor device of claim 1 , wherein said active trenches each includes an upper portion adjacent to a top surface of the substrate and a lower portion below the upper portion such that the upper portion is wider than the lower portion.