Semiconductor device and method of manufacturing the same

A semiconductor device, comprising:

• a n-type FinFET comprising a gate structure between a pair of source and/or drain (S/D) regions, the gate structure comprising:
• a gate dielectric layer;
• a metal filling layer over the gate dielectric layer;
• and
• a work function layer between the gate dielectric layer and the metal filling layer, wherein the work function layer is selected from a material in which a threshold voltage of the n-type FinFET increases as a thickness of the work function layer increases.

A method of manufacturing a semiconductor device, comprising:

• providing a substrate having a first region and a second region;
• forming a first conductive layer over the substrate in the first and second regions;
• forming a bottom material over the first conductive layer by doping a dopant in a base material in an atomic layer deposition (ALD) method, wherein the dopant comprises Al, Ta, W or a combination thereof;
• removing a portion of the bottom material to expose the first conductive layer in the first region and form a bottom layer over the first conductive layer in the second region;
• forming a top material to cover the first conductive layer in the first region and the bottom layer in the second region, wherein a first portion of the top material in the first region is formed as a first work function layer for a first FinFET, and a second portion of the top material in the second region and the bottom layer there-below are formed as a second work function layer for a second FinFET;
• and
• forming a second conductive layer to cover the first and second work function layers.