Lots of articles are written on how to accomplish a successful interview ;but what are the responsibilities of the interviewer towards the job seeker?

Good question!

1. First and foremost: Respect and treat the applicant with dignity regardless of how they look or who they are. 
2. Put the candidate at ease and most people are nervous and need a positive attitude from the interviewer. I personally smile as much as I can to tell the candidate not to feel anxious and relax their defenses which is more conducive to a useful interview. 
3. I share the format of the interview telling them what I plan to do: ask them for an introduction, why they applied, how they see themselved in2 or5 years and then I inform them that I will conduct behavioral-based questions. I tell them they should ask me anything anytime so we dont miss important items. 
4. Once the interview is underway, I always take notes, make sure there is eye contact and probing if necessary. I may interrupt to ask detailed questions. 
5. I end the interview with an anecdote or a fun fact about the company or a topic discussed during the interview. 
6. I inform them about what comes next: if we are still interiviewing, if we are convening for a decision, give them a broad timeline and my business card to call me with any questions. 

There is one opportunity to make a good impression and maybe one day that same candidate may be in a reversed role and interview you, so think of the interview as a relationship building exercise.