As far as I know, none of ctags, etags, or cscope can handle searching for a specific struct member. For example, you cannot find all uses of the Linux kernel's scsi_device's "vendor" field without getting a whole lot of other uses of the field "vendor" of other structs as noise.
Semantic/CEDET is now part of Emacs and does a little bit of that job. I haven't explored the all the features beyond the smart "find tag" (semantic-ia-jump) in C++ feature, though, so I don't know if it may meet your expectations.
