November 21, 2014, anysilicon
In layout stage, the gate level netlist is converted to a complete physical geometric representation. The first step is floorplanning which is a process of placing the various blocks and the I/O pads across the chip area based on the design constraints. Then placement of physical elements within each block and integration of analog blocks or external IP cores is performed. When all the elements are placed, a global and detailed routing is running to connect all the elements together.
Also after this phase a complete simulation is required to ensure the layout phase is properly done.
The file produced at the output of the layout is the GDSII (GDS2) file which is the file used by the foundry to fabricate the silicon. The layout should be done according the silicon foundry design rules.