Method for manufacturing a semiconductor device comprising transistors each having a different effective work function

A method of manufacturing a semiconductor device comprising transistors each having a different work function arranged along a main surface of a substrate, the method comprising:

• providing at least two channel regions in the substrate;
• providing a dielectric layer on the substrate over the at least two channel regions;
• providing openings through the dielectric layer to expose portions of each of the at least two channel regions, thereby defining corresponding gate regions inside the openings and over the at least two channel regions;
• providing a gate dielectric layer on the exposed channel regions of each of the gate regions;
• providing on the gate dielectric layer of each of the gate regions a barrier layer stack each having a different thickness,
• wherein providing the barrier layer stack comprises:
• providing a first barrier layer on the gate dielectric layer of each of the gate regions;
• selectively removing the first barrier layer from a subset of the gate regions while leaving the first barrier layer in at least a complementary subset of the gate regions;
• repeating at least once the processes of:
• providing a subsequent barrier layer in each of the gate regions;
• selectively removing the subsequent barrier layer from a respective subset of the channel regions, while leaving the respective subsequent barrier layer in a respective complementary subset of the channel regions, such that barrier layer stacks having different thickness along different gate regions are provided;
• and
• providing a gate-filling stack of metal layers on the barrier layer stack in each of the gate regions.