Structures and methods to stop contact metal from extruding into replacement gates

Abstract

The methods and structures described are used to prevent protrusion of contact metal (such as W) horizontally into gate stacks of neighboring devices to affect the work functions of these neighboring devices. The metal gate under contact plugs that are adjacent to devices and share the (or are connected to) metal gate is defined and lined with a work function layer that has good step coverage to prevent contact metal from extruding into gate stacks of neighboring devices. Only modification to the mask layout for the photomask(s) used for removing dummy polysilicon is involved. No additional lithographical operation or mask is needed. Therefore, no modification to the manufacturing processes or additional substrate processing steps (or operations) is involved or required. The benefits of using the methods and structures described above may include increased device yield and performance.