Atom size is about 0.1 nm. Processor having about 10^9 transistors and is about 1 cm^2 size. If one transistor is about 50 nm length and wide then in 0.01 m^2 must fit in 10^16 / 500^2 = 4*10^10 transistors. Why going inprocessor going in about 10-100 times less transistors? Perhaps wires between transistors taking many space or transistors in wide are bigger than in length (50 nm * 200 nm, etc).
So what smallest trinsistor size is possible or what will be transistor length in 2020 years? Also I read that in milions silicon atoms must be 1 atom which making pnp, npn. So then transistor can't be bigger than 10 nm *10 nm *10 nm =1000 nm^3 size.
If transistor size decreasing quadraticaly then with 10 nm chip manufacturing will be possible fit in 10^12 transistors in 1 cm^2 (would be 100 times faster than now) . And if manufacturing will be 0.1 nm then in 1 cm^2 will be possible fit in 10^16 transistors (would be milions times faster than now). But transistor size like one atoms is imposible so supose tranzistor 1 nm * 1 nm= 1nm^2. In 1 cm^2 can fit in 10^16 / 10^2 = 10^14 transistors (then it would be about 10000 times fater than now).