Is the stalk of an irreducible scheme at the generic point always a field?

Question

Let $X$ be an irreducible scheme. It can be proved that it has a unique generic point, i.e. there is a unique point $\xi \in X$ such that $\overline{\{ \xi \}} = X$. One can identify $\xi$ as the prime ideal $\sqrt{0} \in Spec(R) = U \subset X$, which is a prime ideal as $U$ is an open subset of $X$ and $X$ is irreducible, hence $U$ is irreducible. Now consider the stalk of $X$ at the point $\xi$. We have that: $$ \mathcal{O}_{X, \xi} = R_{\sqrt{0}}. $$ Now, if $R$ is an integral domain, then $R_\sqrt{0} = R_{(0)} = Frac(R)$, where $Frac(R)$ is the fraction field of $R$, so $\mathcal{O}_{X,\xi}$ is a field. What about the general case? Is it always a field?