Transistor structure having an active region and a dielectric platform region
A semiconductor device is formed having lower gate-to-drain capacitance. The semiconductor device having an active region ( 1300 ) and a dielectric platform region ( 1310 ). A trench ( 80 ) is formed adjacent to a drain ( 20 ) of the semiconductor device to a first depth. The etch process for forming trench ( 80 ) etches the dielectric platform region ( 1310 ) to a first depth. A second trench ( 210 ) is etched in trench ( 80 ) to further isolate areas in the active region ( 1300 ). The etch process for forming the second trench ( 210 ) etches the dielectric platform region ( 1310 ) to form a support structure for the dielectric platform in the substrate. The dielectric platform, the trench ( 80 ), and the second trench ( 210 ) is capped and sealed. The dielectric platform is made approximately planar to the major surface of the substrate by forming the support structure from the first depth to the second depth.
1. A semiconductor device comprising:
a substrate comprising:
at least one active region wherein the active region has a first surface and at least one transistor cell; and
at least one dielectric platform region, the dielectric platform region comprising a support structure in a pin wheel shape wherein the support structure comprises dielectric material, wherein the support structure is formed at a first depth in the substrate below the first surface of the at least one active region to a second depth in the substrate below the first surface of the at least one active region; a dielectric layer overlying the dielectric platform region wherein the dielectric layer caps and seals the dielectric platform region;
a tub region at least partially disposed in the active region at a tub region depth; and
a trench formed in at least a portion of the active region, wherein the trench is formed to a depth equal to or greater than the tub region depth to achieve planar or near planar breakdown in the active region;
wherein the at least one transistor cell is a mesh transistor cell having a centralized source region, a circular shaped gate, and a drain being the substrate.
2. The device as recited in claim 1 wherein the at least one transistor cell is bounded by a first trench of the first depth.
3. The device as recited in claim 2 where the at least one transistor cell has a pedestal region and where a portion of the pedestal region overlies the first trench that bounds the transistor cell.
4. The device as recited in claim 3 where the substrate includes an epitaxial layer of the same conductivity type as the substrate.
5. The device as recited in claim 4 where the second depth extends into the substrate.
6. The device as recited in claim 1 , further including an isolation structure for partitioning areas of the at least one active region comprising;
a first trench having a sidewall and a major surface where the first trench is formed to the first depth;
a second trench formed in the major surface of the first trench where the second trench is formed to the second depth; and
a dielectric layer overlying the major surface of the first trench and capping and sealing the second trench.