Multiple supply voltage is a prevalent and effective technique to balance power and performance. A multiple supply voltage design is divided into voltage islands at physical design, where each island occupies a contiguous physical region and operates at some supply voltage. Given a set of blocks and the timing-safe voltage levels for each block, we simultaneously generate a floorplan and form the corresponding voltage islands based on an efficient and deterministic algorithm. In contrast, prior works usually assign voltages of all blocks either-for a given floorplan-at post-floorplanning or-for an intermediate floorplan-at an iteration of floorplanning. Experimental results prove the superior efficiency of our algorithm under competitive power consumption. Moreover, the results of large design cases further demonstrate the scalability of our algorithm.