Abstract: A boat for a vertical diffusion furnace has an upper disk and a lower disk spaced parallel from each other by a predetermined distance. A pair of first bars, having a plurality of wafer holding slots, face each other along a first center plane extending along a diameter of the upper and lower disks, and connect the upper and lower disks. A pair of second bars also connect the upper and lower disks, and are positioned at a predetermined angle with respect to a second center plane orthogonal to the first center plane. The second bars have a plurality of slots corresponding to the slots of the first bars. A pair of first auxiliary bars are installed adjacent to the pair of first bars to also connect the upper and lower disks. The boat may further have a pair of second auxiliary bars for connecting the upper and lower disks at positions adjacent to the pair of second bars. Also, a pair of horizontal supporting bars connect the first auxiliary bars to the second auxiliary bars.