A semiconductor process chamber includes a susceptor, a base plate surrounding the susceptor, a liner on an inner sidewall of the base plate, and a preheat ring between the susceptor and the base plate and coplanar with the susceptor. The process chamber further includes an upper dome coupled to the base plate and covering an upper surface of the susceptor. The upper dome includes a first section on an upper surface of the base plate and a second section extending from the first section and overlapping the susceptor. The first section includes a first region on the upper surface of the base plate, a second region extending from the first region past the base plate, and a third region extending from the second region with a decreasing thickness to contact the second section.