| US 7,602,014 B2 | ||
| Superjunction power MOSFET | ||
| Edouard D. deFresart, Tempe, Ariz. (US); Robert W. Baird, Gilbert, Ariz. (US); and Ganming Qin, Chandler, Ariz. (US) | ||
| Assigned to Freescale Semiconductor, Inc., Austin, Tex. (US) | ||
| Filed on Apr. 24, 2008, as Appl. No. 12/109,215. | ||
| Application 12/109215 is a division of application No. 11/304196, filed on Dec. 14, 2005, granted, now 7,378,317. | ||
| Prior Publication US 2008/0197409 A1, Aug. 21, 2008 | ||
| Int. Cl. H01L 29/76 (2006.01); H01L 21/336 (2006.01) | ||
| U.S. Cl. 257—328 [257/135; 257/339; 257/341; 257/342; 257/E29.257; 438/283; 438/303; 438/305; 438/268] | 5 Claims |

| 1. A metal oxide semiconductor (MOS) device, comprising:
a semiconductor substrate of a first conductivity type having an upper surface;
a first doped region of the first conductivity type that extends downwardly from the upper surface;
a gate overlying the first doped region and having a gate dielectric on the upper surface, an overlying dielectric layer on
the gate dielectric, and a gate conductor, wherein a lateral extent of the gate extends beyond the first doped region and
over portions of second doped regions that are laterally adjacent to the first doped region at the upper surface;
the second doped regions of a second opposite conductivity type extending downwardly from the upper surface and initially
formed in the substrate beyond the lateral extent of the gate, wherein the first doped region and the second doped regions
meet under the gate after exposure to a high temperature drive process, and wherein a charge equality condition is present
in the first doped region and the second doped regions because a net active impurity concentration Nfirst in the first doped region of lateral length Lfirst and a net active impurity concentration Nsecond in the second doped regions of lateral length Lsecond satisfy a first relationship (Nsecond*Lsecond)=k1*(Nfirst*Lfirst), where k1 has a value in a range of about 0.6<k1<1.4, and also satisfy a second relationship that a depth of the first doped region is about equal to a depth of the second
doped regions; and
a drain region of the first conductivity type located in the semiconductor substrate beneath the first doped region and the
second doped regions, wherein the drain region is separated from the first doped region and the second doped regions by a
portion of the semiconductor substrate that overlies the drain region and is beneath the first doped region and the second
doped regions, and wherein the charge equality condition is not present in the portion of the semiconductor substrate that
overlies the drain region and is beneath the first doped region and the second doped regions.
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