The thermal condition in a rapid thermal processing (RTP) system using circular infrared lamps is systematically studied, for the first time, based on the direct approach model using a ray trace simulation. This study focuses specifically on the temperature profile influenced by the connector, which is the dark region inevitably occupying a small part of the circular infrared lamp. Since the rays emitted from the lamp are distributed over the concentric circle region formed by the cylindrical reflectors, the influence of no radiation from the connector is significantly decreased resulting in the formation of a very shallow valley in the temperature profile of the silicon substrate below the connector. This conclusion is consistent with the actual applicability of the RTP system using the circular infrared lamps for very large diameter silicon substrates.