In some embodiments, the channel region of a FinFET device (e.g., a p-type FinFET device) is doped with a stress-inducing material (e.g., a dopant such as germanium) for the channel to compensate for the threshold voltage variation caused by the diffusion of the dopant (e.g., boron) from the source/drain region into the channel region. In other words, the concentration of the stress-inducing material (e.g., germanium) in the channel region of a fin is formed in accordance with the concentration of the diffused dopant in the channel region of the fin to achieve a uniform threshold voltage. In various embodiments, the stress-inducing material refers to a dopant (e.g., germanium) in the channel region of the FinFET device, which dopant has a lattice constant different from that of a semiconductor material (e.g., silicon) of the channel region, thereby inducing a stress in the channel region. In some embodiments, higher concentrations of the stress-inducing material are used at locations with lower concentrations of the dopant, and lower concentrations of the stress-inducing material are used at locations with higher concentrations of the dopant, which results in a substantially uniform threshold voltage of the FinFET device. In some embodiments, the fin of the FinFET device is formed to have a gradient layer where the concentration of the stress-inducing material (e.g., germanium) increases along a first direction from the top surface of the fin distal a substrate of the FinFET device toward the substrate. The fin may additionally have a buffer layer under the gradient layer, where the buffer layer has a lower concentration of the stress-inducing material than the gradient layer. In addition, the fin may have a first layer with a first uniform concentration between the gradient layer and the buffer layer, and may further have a second layer with a second uniform concentration over the gradient layer, the first uniform concentration being larger than the second uniform concentration. In some embodiments, the fin of the FinFET device is formed to have a first layer with a first uniform concentration over a second layer with a second uniform concentration, the first uniform concentration being smaller than the second uniform concentration. The fin may additionally have a buffer layer under the second layer. In this manner, a concentration of the stress-inducing material (e.g., germanium in this example) may be adjusted to account for the specific dopant profile of a particular design.