Abstract: A robot assembly including multiple independently operable robot assemblies are provided for use in semiconductor wafer processing. The robot assembly includes independent co-axial upper and lower robot assemblies adapted to handle multiple objects. The upper robot is stacked above the lower robot and the two robots are mounted concentrically to allow fast wafer transfer. Concentric drive mechanisms may also be provided for imparting rotary motion to either rotate the robot assembly or extend an extendable arm assembly into an adjacent chamber. Each robot can be either a single blade robot or a dual blade robot. Also provided is an apparatus for processing semiconductor wafers comprising a pre/post process transfer chamber housing multiple independent robot assemblies and surrounded by a plurality of pre-process chambers and post process chambers. Within each process, pre-process and post-process chamber is an apparatus for holding a plurality of stacked wafers.