A silicon tower (42) or boat (84) for removably supporting a plurality of silicon wafers (38, 86) during thermal processing. A preferred embodiment of the tower (10) includes four legs (12) secured on their ends to two bases (14). A plurality of slots (16) are cut in the legs allowing slidable insertion of the wafers and support for them. The legs preferably have a rounded wedge shape with a curved front surface of small radius cut with the slots and a back surface that is either flat or curved with a substantially larger radius. Preferably, the legs are machined from virgin polysilicon formed by chemical vapor deposition from silane. The bases may be either virgin poly or monocrystalline silicon and be either integral or composed of multiple parts. Virgin polysilicon is preferably annealed 1025°C before machining. Silicon parts may be joined by applying a spin-on glass between the parts and annealing the assembly. After assembly, the surface of a tower is subjected to sub-surface working.