Semiconductor device and method of manufacturing the same

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

• providing a substrate comprising a trench;
• forming a gate insulating film in the trench;
• forming a metal oxide film on the gate insulating film, the metal oxide film comprising a metal element;
• forming a gate conductive layer on the metal oxide film;
• and
• heating to diffuse the metal element into the gate conductive layer.

A semiconductor device comprising:

• a substrate comprising a trench;
• a gate insulating film disposed in the trench;
• and
• a gate electrode disposed on the gate insulating film, the gate electrode comprising a gate conductor and a metal element, and a work function of the metal element being less than a work function of the gate conductor.