A method of manufacturing a semiconductor device

The present invention provides a semiconductor device manufacturing method, comprising: providing a substrate having a first region and a second region, each forming a first gate stack in the first region and a second gate stack that a second region, the first gate stack comprising a first dummy gate and the second gate stack comprising a second dummy gate electrode, removing the first gate of the first dummy gate stack forming a first trench and removing the second gate of the second dummy gate stack to form a second trench, forming a first metal layer on the first and second trench, removed a first trench at least a portion of the first metal layer, forming a remaining portion of the second metal layer on the first and second trenches, reflowing the second metal layer, and performing a chemical mechanical polishing. The present invention provides a simple and cost-effective method of having a metal gate is formed for both NMOS and PMOS devices having the appropriate work function gate technology, can reduce the cost and simplify the process.