This paper presents improvements in resizing single crystalline Si wafers by using the dicing technology “Thermal Laser Separation” (TLS). Results of this work support the general need to resize wafers to smaller diameters and will play an important role during the transition to larger wafer diameters as currently projected in the ITRS for 450 mm: Wafers of new sizes have to be easily adapted to fit, e.g., currently available metrology tools. TLS process parameters were developed for resizing Si wafers and to produce demo wafers which were analyzed and compared with current state of the art techniques plasma etching, laser ablation and mechanical wafer sawing. For the first time, circular cuts with diameters up to 300 mm were produced out of 450 mm (thickness: 925 μm) single crystalline Si wafers with TLS. The TLS process results in two important benefits for resized wafers: First, the edge of the new wafer is of higher quality than the edges produced by state of the art resizing techniques. Second, the TLS process is up to 24 times faster than known resizing processes.