A MOSFET device has a funnel-shaped trench etched in a semiconductor substrate. The funnel-shaped trench has flared rim extending from a wider cross section trench mouth at the surface of the semiconductor substrate to a narrower cross section trench body portion which terminates in an epilayer portion of the semiconductor substrate. A gate electrode is disposed in the trench on the flared rim. Source and gate regions of the device abut upper and lower portions of the flared rim, respectively. A drain region of the device, which abuts the narrower cross section trench body portion, is self-aligned with a lower edge of a gate electrode.