In one aspect, an apparatus includes a chamber body, a blocker plate for delivering process gases into a gas mixing volume, and a face plate having holes through which the mixed gas is distributed to a substrate. In another aspect, the face plate may include a first region with a recess relative to a second region. In another aspect, the blocker plate may include a plurality of regions, each region having different hole patterns/geometries and/or flow profiles. In another aspect, the apparatus may include a radiation shield disposed below a bottom of the substrate support. A shaft or stem of the substrate support includes holes at an upper end thereof near the substrate support.