I'm unsure if he actually obtained a Ph. D, but he is an evil scientist. In the lore of the series, he attended Madame Amberly's Academy of Evil at the age of 8 with the other scientist Brio.
Not much is really given about what he actually knows. If he did obtain a PH. D (or in his case, multiple ones would apply), I'd have to guess he'd have them in Particle Physics, and Bio-Engineering. Probably in other fields too, but I'm unsure wich.