A semiconductor device includes a substrate having a NMOS region and a PMOS region; a gate structure extending along a first direction from the NMOS region to the PMOS region on the substrate; and a first contact plug landing directly on the gate structure closer to the PMOS region from a boundary separating the NMOS region and the PMOS region. Preferably, the semiconductor device further includes a first source/drain region extending along a second direction adjacent to two sides of the gate structure on the NMOS region and a second source/drain region extending along the second direction adjacent to two sides of the gate structure on the PMOS region.