Not a foreign language as such, Latin still plays an important part in French society.

Some examples needed.

Then I would say it depends what one is talking about. In some fields some words are predominant in one language because that language has had a lot of natives contributing to that field. As German for philosophy @SimonDéchamps was saying or Italian for music (classical music).

"What do the French do when they need a French word?"

If you mean a word that does not exist in French yet, as is often the case in computer science, they will most of the time use the foreign word, i.e. English as far as computer science is concerned.

But this is highly discouraged by The French Ministère de la Culture that regularly publish in the Journal Officiel French words and phrases to be used instead of their foreign (most of them English) counterparts.

All these words and phrases can be found on FranceTerme.

There's quite a great number of people in France lobbying for the ban of foreign words (mostly English...) in every field, they're those who regret the times when French was the Lingua Franca of the world.

Linga Franca take that as an example of professional jargon in Latin that could have been avoided had I wanted to use a French expression to be understood by the masses. (cf a few lines higher up).