Semillon is the white wine grape responsible for Sauternes. Semillon lends itself to botrytis with it's thin-skinned grapes. However, it also pairs well with oak such as in the white Bordeaux's of Graves and Pessac-Leognan.
It is also a terrific blending partner with Sauvignon Blanc, making up for the Sauvignons lack of body. It is therefore planted widely across the world including Australia and Chile.