A method for manufacturing a semiconductor substrate including a first single-crystalline semiconductor layer and a second semiconductor layer that is in contact with the first semiconductor layer, comprising: an irradiating step of modifying a surface of the first semiconductor layer by irradiating it with one or more types of first impurity (Ar) in a vacuum in order to form an amorphous layer and modifying a surface of the second semiconductor layer by irradiating it with the one or more types of first impurity in the vacuum in order to generate an amorphous layer; a bonding step of bonding the surface of the first semiconductor layer and the surface of the second semiconductor layer to each other in the vacuum in which the irradiating step was executed and thereby producing a semiconductor substrate having a bonded interface; and a heat treating step of applying heat treatment to the semiconductor substrate produced in the bonding step, wherein the first impurity is an inert impurity that does not generate carriers in the first and second semiconductor layers, wherein a second impurity (N, P) that generates carriers in the first and second semiconductor layers is present in a region in the first and second semiconductor layers in which the first impurity is present, the heat treatment is applied such that a region in the vicinity of the bonded interface between the first semiconductor layer and the second semiconductor layer is recrystallized, characterized in that a width of an in-depth concentration profile of the first impurity contained in the vicinity of the bonded interface is narrower after execution of the heat treating step than before the execution of the heat treating step, the heat treatment is applied such that a concentration variation of the first impurity in an in-plane direction in the vicinity of the bonded interface is greater after the execution of the heat treating step than before the execution of the heat treating step, wherein the heat treatment is applied at a maximum temperature of 1500°C or higher in the heat treating step. an irradiating step of modifying a surface of the first semiconductor layer by irradiating it with one or more types of first impurity (Ar) in a vacuum in order to form an amorphous layer and modifying a surface of the second semiconductor layer by irradiating it with the one or more types of first impurity in the vacuum in order to generate an amorphous layer; a bonding step of bonding the surface of the first semiconductor layer and the surface of the second semiconductor layer to each other in the vacuum in which the irradiating step was executed and thereby producing a semiconductor substrate having a bonded interface; and a heat treating step of applying heat treatment to the semiconductor substrate produced in the bonding step, wherein the first impurity is an inert impurity that does not generate carriers in the first and second semiconductor layers, wherein a second impurity (N, P) that generates carriers in the first and second semiconductor layers is present in a region in the first and second semiconductor layers in which the first impurity is present, the heat treatment is applied such that a region in the vicinity of the bonded interface between the first semiconductor layer and the second semiconductor layer is recrystallized, characterized in that a width of an in-depth concentration profile of the first impurity contained in the vicinity of the bonded interface is narrower after execution of the heat treating step than before the execution of the heat treating step, the heat treatment is applied such that a concentration variation of the first impurity in an in-plane direction in the vicinity of the bonded interface is greater after the execution of the heat treating step than before the execution of the heat treating step, wherein the heat treatment is applied at a maximum temperature of 1500°C or higher in the heat treating step.