Semiconductor device and method of manufacturing the same

A semiconductor device, comprising:

• a substrate having an active region;
• and
• first to third transistors on the active region of the substrate, each of the first to third transistors including:
• a dielectric layer on the substrate,
• a metal layer on the dielectric layer, and
• a barrier layer between the dielectric layer and the metal layer,
• wherein each of the first and second transistors further includes a work function layer between the dielectric layer and the barrier layer,
• wherein the barrier layer of the third transistor is in contact with the dielectric layer of the third transistor, and
• wherein a threshold voltage of the second transistor is greater than a threshold voltage of the first transistor and less than a threshold voltage of the third transistor.