What are Voltaire's attitudes to religion?

Voltaire is a deist, so he is not necessarily opposed to religion as a whole, but he does have some very strong negative attitudes toward major organized religions. Overall, Voltaire shows a strong distaste for Christianity, Judaism, and Islam, with different reasons for each, and this is evident in his work Candide.
Above everything else, Voltaire detests Christianity, at one point calling it essentially the worst human creation in the entire world. He believes that it is manipulative and used as propaganda and that it leads to the destruction of reason and freedom. He clearly displays this in the novel with the many instances of his characters encountering evil or corrupt priests, such as those who run the Portuguese Inquisition and who take Cunegonde for a concubine. This sentiment is particularly obvious when Candide visits El Dorado: the town is devoid of priests and is thus a bastion of rationality and intellect.
Additionally, Voltaire harbors a strong hatred and resentment for Jews and is described as one of the most vitriolic haters of Jews in the entire Enlightened era. He typically would lump Judaism in with Christianity, often likening the two faiths' beliefs to one another. He accuses the Jewish people of being greedy and superstitious, and many scholars believe his anti-Semitism stemmed from some personal experience or issue.
Voltaire harbors a lesser distaste for Islam, which he thinks is fairly superstitious. He believes that the Quran is in violation of principles of science and physics. He does, however, praise the accomplishments of various Turks, Arabs, and Muslims, showing something of a preference for Islam over the other Abrahamic religions.
Voltaire is actually particularly fond of the beliefs of both Buddhism and Confucianism, neither of which are, ironically, theistic religions by nature. He appreciates the moral and mental aspects of both of these faiths. It seems, however, that he was unwilling to decide on a deity he personally believed in, even though he didn't necessarily deny the existence of one.