Power MOSFET having a trench gate electrode

A power MOSFET comprising: a semiconductor substrate (204) of a first conductivity type; an epitaxial layer (202) formed on a surface of the substrate, the epitaxial layer including a portion in contact with the substrate and being doped to a first conductivity to a concentration lighter than a doping concentration of the substrate; a trench (208) formed at a surface of the epitaxial layer, the trench extending into the epitaxial layer, the trench having a plurality of sections which define a MOSFET cell; a gate (206) formed in the trench; a source region (216) of the first conductivity type located adjacent a sidewall of the trench at a surface of the epitaxial layer in the MOSFET cell; a body (218) of a second conductivity type located in the epitaxial layer, the body adjoining the source region in the MOSFET cell and comprising a channel region adjacent the sidewall of the trench; a drain of the first conductivity type comprising the substrate and the portion of the epitaxial layer, the drain forming a first portion of a PN junction with the body, the body being located above the first portion of the PN junction, the drain being located below the first portion of the PN junction, the entire PN junction being located at a level above a bottom of the trench, the first portion of the PN junction near the sidewall of the trench having a first breakdown voltage; and a heavily-doped region (222) of the second conductivity type within the body at a central region of the MOSFET cell, the dopant concentration of the heavily-doped region being greater than a doping concentration of the body, the heavily-doped region forming a second portion of the PN junction with the drain such that the second portion of the PN junction at the central region of the MOSFET has a second breakdown voltage, the second breakdown voltage being lower than the first breakdown voltage.