There are three main limits, and several secondary ones.<p>The big one is heat.  As densities go up, so do power consumption and heat dissipation for active cells.  Inactive cells are OK, which is why the highest density devices are now flash memories.  That doesn&#x27;t help CPUs.<p>The next is fab cost.  As someone else pointed out, state of the art fabs cost billions now, and there are fewer ones with each generation.<p>Finally, of course, sizes are getting close to the atomic level.<p>Secondary limits include electromigration (the atoms won&#x27;t stay where you put them as they&#x27;re pulled on by electric fields) and even X-rays not being short enough for mask etching.<p>Heat is the biggest problem.  CPUs aren&#x27;t that big; you can fit a thousand in a shoebox if you can cool them.  The Bitcoin ASIC business is a worst case.  Those devices need no external memory and very little I&#x2F;O, but most of the gates toggle on every cycle.  Mining farms are now located in cold climates near cheap power stations.