The present invention relates to semiconductor devices, and more specifically, to a semiconductor device including work function metal layers to control threshold voltages.
As trends to increase semiconductor device scaling continue, conventional semiconductor devices have relied on multiple work function metal (WFM) layers to achieve threshold voltage variation. However, conventional fabrication processes for providing increased scaled semiconductor devices that include multiple WFM layers have proven to be complicated and difficult. For example, increased fabrication processes are required as the number of WFM layers increase. In addition, residual work function metal removal processes can alter the threshold voltage provided by the WFM layer.