Methods for producing near zero channel length field drift LDMOS

摘要

Adverse tradeoff between BVDSS and Rdson in LDMOS devices employing a drift space adjacent the drain, is avoided by providing a lightly doped region of a first conductivity type (CT) separating the first CT drift space from an opposite CT WELL region in which the first CT source is located, and a further region of the opposite CT (e.g., formed by an angled implant) extending through part of the WELL region under an edge of the gate located near a boundary of the WELL region into the lightly doped region, and a shallow still further region of the first CT Ohmically coupled to the source and ending near the gate edge whereby the effective channel length in the further region is reduced to near zero. Substantial improvement in BVDSS and/or Rdson can be obtained without degrading the other or significant adverse affect on other device properties.

主权项

1. A method for forming a field LDMOS device, comprising:
providing a semiconductor (SC) body with a first conductivity type (CT) semiconductor (SC) region of a first thickness extending therein from a first surface thereof; forming a WELL region of a second, opposite, opposite conductivity type (CT) in the semiconductor (SC) region; forming a first conductivity type (CT) drift space laterally spaced from the WELL region by a part of the first semiconductor (SC) region; forming over the first surface an insulated gate with a first gate edge and a second gate edge; forming a further region of the second conductivity type (CT) so that it lies partly in the WELL region and extends under the first gate edge and has a further region edge in the part of the first semiconductor (SC) region; forming a still further region of the first conductivity type (CT) in the further region and having a still further region edge separated from the further region edge by a length within the further region corresponding to a field inducible channel of the first CT adapted to be formed by the gate within the further region; and providing a source of the first conductivity type (CT) in Ohmic contact with the still further region, and a drain of the first conductivity type (CT) in the drift space beyond the second gate edge.