An CMOS device comprises a plurality of NMOS transistors and a plurality of PMOS transistors, each of which comprises a gate stack constituted of a gate insulating layer and a gate metal layer on a substrate, a source/drain region in the substrate on both sides of the gate stack and a channel region below the gate stack, wherein the gate metal layer of each NMOS transistor comprising a first barrier layer, an NMOS work function adjusting layer, a second barrier layer, and a filling layer, and wherein the gate metal layer of each PMOS transistor comprising a first barrier layer, a PMOS work function adjusting layer, an NMOS work function adjusting layer, a second barrier layer, and a filling layer, and wherein the first barrier layer in the gate metal layer of the NMOS transistor and the first barrier layer in the gate metal layer of the PMOS transistor contain a doping ion to finely adjust the work function. The semiconductor device and the method for manufacturing the same according to the present disclosure utilize the sacrificial layer to diffuse impurity to the barrier layer so that the adjusting accuracy of the threshold voltage may be effectively improved, thereby facilitating in improving the whole performance of the device.