A method of thermally oxidizing a Si fin to form an oxide layer over the Si fin and then forming an ALD oxide layer over the oxide layer and resulting device are provided. Embodiments include forming a plurality of Si fins on a Si substrate; forming a dielectric layer over the plurality of Si fins and the Si substrate; recessing the dielectric layer, exposing a top portion of the plurality of Si fins; thermally oxidizing surface of the top portion of the plurality of Si fins, an oxide layer formed; and forming an ALD oxide layer over the oxide layer.