The author is responsible in the first place. If the supervisor is not the author but was aware of plagiarism in the paper and did not warn the student neither did he/she act to prevent submission, he/she shares the responsibility too...

It appears that only authors are responsible if they deliberately did it.

Well, it's against professional ethics, so everyone who knew and did not prevent the publication, is responsible. What kind of responsibility is this, just moral or administrative, it's another question...

I would recommend to read this article for a deeper insight into the problem:

http://www.bmartin.cc/pubs/84jtea.pdf

Of course he is !!

I think if the paper has been published by Ph. D. candidate in knowledge of supervisor then both are equally responsible otherwise only candidate is responsible.

yes of course

Joint responsibility of research scholar and supervisor ...

Research Scholar and Research Guide