Gate resistance reduction through low-resistivity conductive layer

A structure comprising:

• a first gate stack comprising:
• a first gate dielectric;
• and
• a first gate electrode comprising:
• a first work-function layer over the first gate dielectric;
• a first blocking layer comprising titanium nitride over and contacting the first work-function layer;
• a first metal layer over and contacting the first work-function layer and the first blocking layer, wherein an entire top surface of the first blocking layer is in contact with the first metal layer;
• and
• a second gate stack wider than the first gate stack, the second gate stack comprising:
• a second gate dielectric;
• and
• a second gate electrode comprising:
• a second work-function layer over the second gate dielectric;
• a second blocking layer comprising titanium nitride over and contacting the second work-function layer;
• a filling-metal region over the first blocking layer;
• and
• a second metal layer, wherein top surfaces of the second blocking layer are in physical contact with both of a first bottom surface of the filling-metal region and a second bottom surface of the second metal layer, wherein the filling-metal region and the second metal layer form a distinguishable interface in between.

A structure comprising:

• a gate spacer;
• a gate stack comprising:
• a gate dielectric;
• a plurality of conductive layers on the gate dielectric, wherein the plurality of conductive layers comprise a lower layer and a topmost layer over the lower layer, and the topmost layer has a lower resistivity than the lower layer;
• a metal layer over and contacting top surfaces of the plurality of conductive layers, wherein a first sidewall of the metal layer contacts a second sidewall of the gate dielectric, and wherein the metal layer and the topmost layer comprise different materials;
• a dielectric filling region comprising:
• a first portion over and contacting the gate spacer, wherein a part of the first portion is lower than a first top end of the gate spacer;
• and
• a second portion over and contacting the metal layer;
• and
• a source/drain region aside the gate spacer.