Dear Ahmed, 

 There can be a number of topics on CMOS VLSI/ ULSI circuits. You may design any of digital circuit used in digital electronics such as ALU or a microcontroller for low power applications. Plenty of books available on CMOS IC design can be used for reference you may also do literature survey for particular topic of your intrest to find cutting edge research topic of your choice. This option is far better than a ready made suggested topic. This will provide you flexibility and you may match your intrest also for better outcome. All the best.

Thanks for your answer

I have already read in low power cmos circuit desgin in both analog and digital 

I found there are several techniques from system level to transistor level in digital desgin 

And alot of circuit techniques in analog desgin .

What i need to know what are the circuits that already consumes high power consumption in the vlsi industry .