Disclosed are embodiments of a trigate field effect transistor that comprises a fin-shaped semiconductor body with a channel region and source/drain regions on either side of the channel region. Thick gate dielectric layers separate the top surface and opposing sidewalls of the channel region from the gate conductor in order to suppress conductivity in the channel planes. A thin gate dielectric layer separates the upper corners of the channel region from the gate conductor in order to optimize conductivity in the channel corners. To further emphasize the current flow in the channel corners, the source/drain regions can be formed in the upper corners of the semiconductor body alone. Alternatively, source/drain extension regions can be formed only in the upper corners of the semiconductor body adjacent to the gate conductor and deep source/drain diffusion regions can be formed in the ends of the semiconductor body.