“Charlie’s just done,” says a set source. “And he’s quietly telling his friends he’s not coming back.” Although sources say the network hoped the star would sign a new contract for an eighth season, Sheen recently turned down the offer. “He wants to move on,” says a friend of the actor, whose contract is fulfilled after he tapes this season’s 22nd episode. “Leaving is 100 percent his idea.”TMZ's sources, however, see Sheen's words as a routine negotiating tactic. “Men” and its Monday-night partner, “The Big Bang Theory,” are CBS’ highest-rated series and the highest-rated sitcoms on TV: