I think texts like the Torah or the Bible describe demons as malevolent spirits that come from a central deity, like "God". Fallen angels would fall into this category, so there would be no distinction between fallen angels and demons. In this case, a demon would not be created "evil", since theoretically, only "good" can come from "God", and an evil spirit would have to be a good spirit gone bad.
However, in other religions, good spirits and malevolent spirits are created as unique races, not one race with differing alignments.
For example, Azazel, Belial, and Lucifer are fallen angels because they have lost their way. They can "redeem" themselves, be forgiven, and return to their former state. A spirit born evil, like those in eastern mysticism, does not have this option.