SEMICONDUCTOR DEVICE HAVING WORD LINE EMBEDDED IN GATE TRENCH

An apparatus that includes a semiconductor substrate having first and second gate trenches arranged in parallel and extending in a first direction, and first and second gate electrodes embedded in the first and second gate trenches, respectively, via a gate insulating film. Each of the first and second gate electrodes includes a first conductive film located at a bottom of the respective first and second gate trenches and a second conductive film stacked on the first conductive film. The second conductive film included in a first portion of the second gate electrode is thinner than the second conductive film included in a first portion of the first gate electrode which is arranged adjacently to the first portion of the second gate electrode in a second direction crossing to the first direction. The second conductive film is lower in work function than the first conductive film.