In a university, intellectual property may be jointly owned by you, the university, and the sponsor. The question of ownership is complicated by the fact that companies funding research have their own policies. At VPI, a company sponsoring research can pay a higher overhead rate for sole ownership of the research results. If you leave the univerity to develop a research idea into a commercial product, then the university is likely to have a right to part of the profits. Many universities have organizations to help researchers commercialize their ideas.
The policy may also control who owns an idea that you develop at home. (For example, you may use some piece of the employer's equipment at home.)