High frequency switching MOSFETs with low output capacitance using a depletable P-shield

摘要

Aspects of the present disclosure describe a high density trench-based power MOSFETs with self-aligned source contacts and methods for making such devices. The source contacts are self-aligned with spacers and the active devices may have a two-step gate oxide. A lower portion may have a thickness that is larger than the thickness of an upper portion of the gate oxide. The MOSFETS also may include a depletable shield in a lower portion of the substrate. The depletable shield may be configured such that during a high drain bias the shield substantially depletes. It is emphasized that this abstract is provided to comply with rules requiring an abstract that will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

主权项

1. A MOSFET device, comprising:
a semiconductor substrate of a first conductivity type wherein the substrate includes a lightly doped epitaxial region in a top portion of the substrate; a body region of a second conductivity type formed in a top portion of the semiconductor substrate, wherein the second conductivity type is opposite the first conductivity type; a plurality of active device structures formed from the semiconductor substrate and body region, wherein each active device structure comprises a gate electrode insulated with a gate oxide, wherein an upper portion of the gate oxide is a thickness T1 and a bottom portion of the gate oxide is a thickness T2, wherein T2 is greater than T1; a depletable shield of the second conductivity type formed in the semiconductor substrate at a depth at least partially below a bottom surface of one or more trenches, wherein the depletable shield is electrically connected to the body region; an insulative layer over a top surface of the body region; a conductive source metal layer formed over the insulative layer; and one or more electrical connections that connect the source metal layer with the one or more source regions.