In the US, according to the first ammendment scientists can believe in any religion or not to, so yes a scientist can be religious or not, it is up to them.
To say that science is not faith based in some instances, is false IMO. There are not very many theories that don't have an assumption or two in them. Since we don't know what caused the assumption(or it wouldn't be an assumption) just that it works in the equation, we have to use a little faith(less and less the more times it works) that the theory is valid. It seems that with the big bang one person states people that believe something was behind it are basing that on faith because they have no proof, but another states that since we have no proof that something caused it, then it couldn't have happened that way, which is faith based also since they can't prove that something didnt cause the big bang. I would agree with noblegas as to the fact that we don't know for sure one way or the other, anyone claiming other wise is basing some beliefs on faith(isnt that basically what a belief is, something you believe to be true but can't completely prove(faith based), a truth is something you can prove to be true(not faith based) but even that is subjective to the information available at the time, if we don't have complete information what may seem to be a truth one day might be proven wrong the next when more information is discovered, which means that even the truth had elements of faith involved.