Hi,
every digital electronic circuit has it´s frequency limits.
You can find this information in the datasheets.
so if a microcontroller is specified to run up to 20MHz you can not run it with 200MHz.
***
all your questions refer to the production process, density, chip area, power dissipation....
with smaller structures (modern i7 models go down to 22nm) you can increase the number of transitors and the clock speed.
This makes up to 2 600 000 000 transistors on 435 mm^2.
All the PC processor manufacturers work toimprove their limit in case of yield, density and clock speed.
It is all not that easy as it seems...
Klaus