Do you have to have a PhD to be a "research scientist"? I'm graduating from my master's degree at MIT this summer and I have a chance to stay for another year as an employee in my current lab while I apply for PhD programs. I'd love to do that because I love the current grant I am working on, I love the topic, the people and the PI. 

My only hesitation is that there seems to be very limited titles in academia for one who is not a graduate student and does not have a PhD. The truth is, I do not want to be a "lab tech." I want to start becoming autonomous in the field I did my master's and becoming a lab tech is the exact opposite of being an independent researcher (based on my understanding).

I feel like if I start my year-long employment with the agreement with my PI that I'll continue work on my current research but with the "lab tech" title, the post-doc who supervises my work will treat me like a lab tech!

Therefore, I'd like to be a "research scientist" for the next year, but do I have to have a PhD for that? Or, what other titles are there besides a lab tech for people who wants to do research without a PhD in academia?
Titles depend on institution. In industry, you can be a "research scientist" with no particular degree. In a university, a "research scientist" may be a catch-all term for scientific employees, or it may be a parallel track with similar prestige to a professorship (with similarly high standards). I do not know what MIT's system is. 

Your job responsibilities will depend on your boss (advisor) far more than your title. If your advisor is on board with you continuing your current research, then great; this will be true regardless of your title. If they are doing you a favor allowing you to remain employed while you apply for PhD programs, then they may expect you to do "lab tech" type work. 

It's certainly a good idea to discuss your title, responsibilities and goals with your advisor before accepting the position. But I wouldn't be too concerned about the title. If this were a permanent position for you, I might agree that "lab tech" would be an unfortunate title, and might have unfortunate implications about your ability to participate in original research (especially since you would have to consider your position if your supervisor moves on). But since this is just a temporary stop-gap until grad school, I would focus this conversation on your responsibilities and goals.