I have just read about "German Phd in industry" in the site, "Research-in-Germany". It says that even if I get a phd position in industry, I need a university professor to supervise my research and award the doctor degree.
*So, I wonder if a company accept me, I should work in the company or University (Physically, I often need to go to the company (or not), and no need to go to University).
In many German universities, traditionally the PhD process is only concerned with what happens once you show up with your completed thesis manuscript in triplicate. Before that moment, there are little to no requirements - where I was, the only thing required was a letter from a Professor of this university saying "I agree to supervise X", submitted at least a year before the actual thesis. Therefore, it is trivial from an administrative standpoint to do a PhD in a company: you, Prof, and Boss agree on how to handle things among yourselves. This could be working all day in the company, and then writing it up on the weekends with the advice of Prof, it could be doing half time in the company and half time in the lab, it could be whatever seems good as long as it results in work of an adequate level (and earns you enough money to survive). The university only cares that at the end, you wrote a tome that a jury of three professors agrees is worth a PhD.
Of course, the devil is in the details. This might depend a lot on the field, but my previous lab had a collaboration with a Fraunhofer research institute, and I heard that even for employees of such a research-oriented company, where the possibility to acquire a PhD at the same time is baked into the contract and part of the attraction, the pressures of work life were such that many did not manage to make sufficient research contributions, and left without a degree when their time was up.
I'm from Austria but the system is the same.
Only universities can award PhDs, so no matter where or how you do your PhD you need a supervisor at a university and you need to hand the thesis in at your university, get reviews like every other student has to and defend your thesis at that university. This is always the same.
In principle you can do your thesis wherever you want or got a position, as long as it's research based and your supervisor (and the dean of studies) approves the topic. The actual details on how everything works depend on the industry partner and the university, but there are two main cases.
1) You are doing your research directly at the company, in that case you don't need to be at the university except maybe for some courses you have to take and of course meetings with your supervisor. Usually you enter some kind of "PhD contract" that says you should meet your supervisor every X months or something like that. In this case you are usually paid by the company to do research and the university might not be involved.
2) The university is working together with a company on a research project, in that case you will work wherever you are needed. This is often the case if (smaller) companies need help in projects they cannot or don't want to do in house. In that case you might be paid by either the university or the company.
Be aware that in both cases you have to write a thesis which will be publicly available, which can be a problem when working with companies. There's usually the possibility to "lock" the thesis for a certain amount of time (some years) to get patents for example, but all of this is something you need to clarify beforehand! This is extremly important!
There was enough and correct said about the situation with thesis submission and formalia of the PhD awarding. I am tackling this question from a different viewpoint.
Basically, if you work at the university, you work directly under your supervisor, the university professor. Either, you are paid from state funds (which you are not), or you are paid from a third-party funding.
Most third-party fundings are basically "your supervisor get a sack of money". So, while your research topic might be shaped by the third party, your boss is still the supervisor, you work for him.
Now, I would imagine that many companies would not like this. So, in most cases of an industry-based PhD project, you work for the company. The company might be nice enough to allow you to collaborate with your supervisor on your job results academically. But this is not a given. (In this case you basically do your PhD on weekends.)
The only exception to this view is when the company plays the role of a third-party fund. So, it's basically, "here is a ton of money" for your supervisor, there is an interest for the research in the company, and there are capabilities to do it at your supervisor's lab. Where do you work depends now on some agreements between to sides, but you might have a choice.
In most cases, however, you cannot choose. You are either bounded to your supervisor (because the money for your position are with him and your university). Or you are chained to your company's chair (because they pay you and your PhD is at best a byproduct and at worst your own problem entirely).
