No, it depends on state, and it is (in all states?) more subtle than that. Speaking broadly, the intruder must enter unlawfully and/or forcibly, and you must have a reasonable belief they intend to commit some felony. Generally law merely creates a presumption that the resident had a reasonable belief that the force was necessary to protect themselves (or stop said felony), and this could be refuted in court.

Generally speaking, if you do not have a reasonable belief that such force is necessary, lethal force is not lawful, even if someone is breaking into your home. However, in that case, one might nevertheless escape conviction for use of lethal force thanks in part to that presumption.

http://en.wikipedia.org/wiki/Castle_doctrine

This is false. Lethal force is legal only under very specific conditions in most of the US, although there are exception where states have enacted a Castle doctrine type of law (Texas is the most obvious example here).

It's actually a majority of states (31) now. These laws don't simply mean you can shoot anyone who trespasses in your house; the entry must be forceful and you must believe that the person intended to seriously harm someone in the house or remove someone against their will. The castle doctrine simply creates a presumption that, barring evidence to the contrary, someone who "unlawfully and forcibly" enters a home plans to harm the people inside.

I think self defense easily fits the scenario of having a masked guy with crowbar in my home.