Why doesn't a diode or transistor get neutral?
If there are extra electrons on n-type silicon (doped), why don't they just flow through ground maybe and N part becomes neutral. 


The key thing that's glossed over in your description of the pn junction, is that when we say there are "extra electrons" in the n-region, we're not mentioning where they come from. These electrons come from "donor" impurities in the silicon crystal. When these impurity atoms give up their electrons, they become positively charged. However these positive charge sites aren't mobile so they don't contribute to conduction through the diode.

The balance between the mobile free electrons and the immobile positively-charged donor sites actually gives the n-region a neutral charge overall.

Similarly, in the p-region, we have mobile positively charged holes in balance with immobile negatively charged acceptor impurity sites.

If all the "extra electrons" were to drain out of the n-side of the pn junction, the n-region wouldn't be left neutral, it would be left with a large postive charge from the remaining donor sites.