who should I contact for the Faculty interview follow up: Department head or Search committee? One month ago, I have done a campus interview for a possible academic job. Now I am thinking to send a followup e-mail. I would appreciate to let me know whom should I include in the follow up e-mail. 

When they invite me for the interview, there was a search committee chair and 5 other search committee members. However, during my campus visit, I met more than 20 faculty members including the department head and school dean.

What I am thinking to do is to send an e-mail for the department head and cced to all the search committee members including the chair. Is this the correct approach? 

Or should I send a follow up e-mail to the search committee chair and cced to the committee members.

Thanks
If your goal is simply to thank them for hosting you and meeting with you, I think it's really up to you to choose who to include.

However, I'm guessing that your main goal is to get a reply with some kind of update about your application status.  In that case, I would send a message with only one recipient.  The reason is simple: if there are multiple recipients, it's unclear who should respond and since they are busy people they may each hope that one of the other recipients will respond.  

As for who that single recipient should be, I would write to the same person that invited you for the interview.  That message may have officially come from the department or committee, but there is a single person who sent it; that person is certain to know the status of the search and is the person most likely to reply promptly to you.

In case all the invitation correspondence was with an administrator and not a professor, then the search committee chair is a good choice.