Methods of forming doped transition regions of transistor structures are provided herein. The methods include, for instance: providing a first semiconductor material including a dopant over a source/drain region of the transistor structure; providing a second semiconductor material including the dopant over the first semiconductor material, where the second semiconductor material is different from the first semiconductor material; and, where providing the second semiconductor material is performed at a temperature sufficient to diffuse the dopant from the first semiconductor material through the source/drain region into a portion of a channel region of the transistor structure. The portion of the channel region into which the dopant from the first semiconductor material diffuses forms the doped transition region.