An integrated circuit includes a transistor of a first type with a first gate electrode and a transistor of a second type with a second gate electrode. The first gate electrode is formed in a first gate groove that is defined in a semiconductor substrate, and the second gate electrode is formed in a second gate groove defined in the semiconductor substrate. The first gate electrode completely fills a space between two adjacent first isolation trenches, and the second gate electrode partially fills a space between two adjacent second isolation trenches, with substrate portions being arranged between the second gate electrode and the adjacent second isolation trenches, respectively.