A device comprises a first transistor, a second transistor, a first contact, and a second contact. The first transistor comprises a first gate structure, first source/drain regions on opposite sides of the first gate structure, and first gate spacers spacing the first gate structure apart from the first source/drain regions. The second transistor comprises a second gate structure, second source/drain regions on opposite sides of the second gate structure, and second gate spacers spacing the second gate structure apart from the second source/drain regions. The first contact forms a first contact interface with one of the first source/drain regions. The second contact forms a second contact interface with one of the second source/drain regions. An area ratio of the first contact interface to top surface the first source/drain region is greater than an area ratio of the second contact interface to top surface of the second source/drain region.