A power MOSFET includes a semiconductor substrate with an upper surface, a cavity of a first depth in the substrate whose sidewall extends to the upper surface, a dielectric liner in the cavity, a gate conductor within the dielectric liner extending to or above the upper surface, body region(s) within the substrate of a second depth, separated from the gate conductor in a lower cavity region by first portion(s) of the dielectric liner of a first thickness, and source region(s) within the body region(s) extending to a third depth that is less than the second depth. The source region(s) are separated from the gate conductor by a second portion of the dielectric liner of a second thickness at least in part greater than the first thickness. The dielectric liner has a protrusion extending laterally into the gate conductor away from the body region(s) at or less than the third depth.