A method for fabricating a semiconductor crystal that has a first step for forming a semiconductor crystal layer (202) that contains carbon atoms and at least one kind of Group IV element other than carbon on a substrate (201), a second step for adding an impurity that is capable of reacting with oxygen to the semiconductor crystal layer (202), and a third step for removing the carbon atoms contained in the semiconductor crystal layer (202) by reacting the carbon with the impurity. This method makes it possible to fabricate a semiconductor crystal substrate in which the concentration of interstitial carbon atoms is satisfactorily reduced, thus resulting in excellent electrical properties when the substrate is applied to a semiconductor device.