Senator McCarthy did not start the Committee on Un-American Activities -- it was a standing committee, and it was a House Committee, not a Senate Committee.
The committee set up to investigate McCarthy's charges was the Tydings Committee, named after the Senator from Maryland.
http://en.wikipedia.org/wiki/Tydings_Committee
With the beginning of his second term as senator in 1953, McCarthy was made chairman of the Senate Committee on Government Operations.
The Committee on Government Operations included the Senate Permanent Subcommittee on Investigations, which McCarthy used to continue his witch hunt against Communists.
http://en.wikipedia.org/wiki/Senate_Permanent_Subcommittee_on_Investigations