When does a researcher become a computer scientist?
When do you call a researcher a computer scientist?


A runner is someone who runs; a writer is someone who writes; a researcher is someone who does research; a computer scientist is someone who does computer science.  So if you're doing computer science research, I will call you a computer scientist and a researcher, even if you aren't yet published, even if you work full-time as a plumber, even if you're still in junior high school.


  Is there a certain level of experience after which the researcher will be called a computer scientist?


No.  There is nothing you can do to make other people call you anything.

But to call yourself a computer scientist, the only requirement is that you are doing computer science.  So in that sense, yes, there is a certain required level of experience: More than zero.