A wafer boat system comprises a carrier and a plurality of holder rings configured to support a wafer in the carrier. Each of the holder rings has an annular body and ring projections projecting from said annular body for contact with the wafer. At the ring projections, a local surface area of the annular body is small compared to a circumferential average or median of the local surface area of the annular body, in particular so as to at least partly compensate for a surface area of the respective ring projection, thereby promoting evenness of vapor deposition on wafers supported on the holder rings in the carrier. The reduced local surface area is preferably realized by a relatively large inner radius of the annular body at the ring projection. The carrier may provide a reference structure for automated wafer positioning.