Patent ID: 7485909

Claim:
A semiconductor device comprising: a semiconductor substrate formed with a trench having a sidewall including a middle point, the trench including a first part extending from a surface of the semiconductor substrate to the middle point of the trench and having a diameter that is gradually reduced as the first part extends deeper from the surface of the semiconductor substrate to the middle point of the trench, the trench including a second part that is deeper than the middle point of the sidewall and that has a larger diameter than the middle point of the sidewall; an electrically conductive film formed in an interior of the trench so as to be located lower than the middle point of the sidewall, the conductive film having a planarized upper surface; and a collar insulating film formed over the conductive film and the sidewall of the trench so as to extend through the middle point of the sidewall along the sidewall, wherein the electrically conductive film with a void includes a first conductive film located below the middle point of the sidewall relative to an inside of the trench and including an upper part formed with a recess and a discrete second conductive film formed in the recess of the first conductive film.