A method of producing a silicon semiconductor substrate, the method comprising: a first epitaxial layer forming step of forming a first epitaxial layer by introducing a dopant gas of a first conductivity type to a semiconductor substrate of the first conductivity type; a trench forming step of forming a trench in the first epitaxial layer; and a second epitaxial layer forming step of forming a second epitaxial layer on the first epitaxial layer and in the trench, by introducing a dopant gas of a second conductivity type that is different from the first conductivity type at a predetermined first dopant gas flow rate, in an atmosphere of a predetermined first temperature; a third epitaxial layer forming step of forming a third epitaxial layer to fill up the trench, by introducing the dopant gas of the second conductivity type to the second epitaxial layer at a second dopant gas flow rate that is greater than the first dopant gas flow rate, in an atmosphere of a second temperature that is lower than the first temperature; a fourth epitaxial layer forming step of forming a fourth epitaxial layer by introducing the dopant gas of the second conductivity type to the second epitaxial layer and the third epitaxial layer at a third dopant gas flow rate that is lower than the second dopant gas flow rate, in an atmosphere of a third temperature that is higher than the second temperature, wherein the second conductivity type is p-type, and the epitaxial layers are formed by chemical vapor deposition and the dopant concentrations of the second epitaxial layer, the third epitaxial layer and the fourth epitaxial layer have a difference between each other not greater than ±5%. a first epitaxial layer forming step of forming a first epitaxial layer by introducing a dopant gas of a first conductivity type to a semiconductor substrate of the first conductivity type; a trench forming step of forming a trench in the first epitaxial layer; and a second epitaxial layer forming step of forming a second epitaxial layer on the first epitaxial layer and in the trench, by introducing a dopant gas of a second conductivity type that is different from the first conductivity type at a predetermined first dopant gas flow rate, in an atmosphere of a predetermined first temperature; a third epitaxial layer forming step of forming a third epitaxial layer to fill up the trench, by introducing the dopant gas of the second conductivity type to the second epitaxial layer at a second dopant gas flow rate that is greater than the first dopant gas flow rate, in an atmosphere of a second temperature that is lower than the first temperature; a fourth epitaxial layer forming step of forming a fourth epitaxial layer by introducing the dopant gas of the second conductivity type to the second epitaxial layer and the third epitaxial layer at a third dopant gas flow rate that is lower than the second dopant gas flow rate, in an atmosphere of a third temperature that is higher than the second temperature, wherein the second conductivity type is p-type, and the epitaxial layers are formed by chemical vapor deposition and the dopant concentrations of the second epitaxial layer, the third epitaxial layer and the fourth epitaxial layer have a difference between each other not greater than ±5%.