Semiconductor device and method of manufacturing the same

A semiconductor device, comprising:

• a semiconductor substrate;
• a source region and a drain region being formed over an upper surface of the semiconductor substrate and each being of p conductive type;
• a gate electrode formed over the semiconductor substrate between the source region and the drain region through a gate insulating film;
• and
• a first insulating film embedded in a trench formed over the upper surface of the semiconductor substrate between the gate insulating film and the drain region in a gate-length direction of the gate electrode,
• wherein part of the gate electrode is formed immediately above the first insulating film, and
• wherein the gate electrode includes:
• a metal film located immediately above the upper surface of the semiconductor substrate between the first insulating film and the source region;
• and
• a semiconductor film electrically coupled to the metal film and located between the metal film and the source region in the gate-length direction.

A method of manufacturing a semiconductor device, comprising the steps of:

• (a) providing a semiconductor substrate;
• (b) forming a source region of p conductive type and a drain region of p conductive type over an upper surface of the semiconductor substrate;
• (c) forming a first trench in the upper surface of the semiconductor substrate and forming a first insulating film embedded in the first trench;
• (d) forming a gate insulating film covering the upper surface of the semiconductor substrate between the first insulating film and the source region;
• (e) after the step (d), forming a semiconductor film immediately above the first insulating film between the source region and the drain region and immediately above the upper surface of the semiconductor substrate between the first insulating film and the source region;
• (f) exposing the upper surface of the semiconductor substrate between the first insulating film and the source region from the semiconductor film by forming a second trench penetrating the semiconductor film;
• and
• (g) forming a gate electrode including a metal film and the semiconductor film by forming the metal film filling the second trench,
• wherein the gate electrode, the source region, and the drain region form a field-effect transistor.