Hi Vadim -
There are several different "layers" to the design of switches - are you asking about designing at a schematic level, or layout level (metal/via layouts to achieve low Rdson and satisfying EM rules, sense device design, bond pads locations, etc.), or basic device level (doping profiles, process integration, optimizing resistance vs breakdown voltage, etc.)?
Are you using any of the foundry technologies? If so - your foundry should provide you with some basic design/layout ideas...
Max