A method of forming a buffer layer on a silicon carbide substrate , comprising: in a first step, forming a silicon carbide film on a surface of the silicon carbide substrate ; in a second step, treating the surface of the silicon carbide film with predetermined ions so that a top doped region of the silicon carbide film close to a top surface of the silicon carbide film is doped with the predetermined ions, so as to increase concentration of the predetermined ions in the top doped region , the top doped region has a thickness of less than 10 nm, and the thickness of the top doped region is less than a thickness of the remaining portion of same silicon carbide film under the top doped region ; in a third step, forming another layer of silicon carbide film on the silicon carbide film ; and repeating the second and third steps at least once to successively form at least two layers of silicon carbide films which make up the buffer layer , wherein the silicon carbide substrate is successively subject to the first to third steps within the same process chamber, wherein the first step comprises forming the silicon carbide film by introducing a carbon-source gas and a silicon-source gas to the process chamber, and wherein the second step comprises stopping the introduction of the carbon-source gas and the silicon-source gas and then doping the top surface of the silicon carbide film by introducing a source of the predetermined ions to the process chamber, and wherein the third step comprises stopping the introduction of the source of the predetermined ions and then growing the other silicon carbide film by again introducing the silicon-source gas and the carbon-source gas. in a first step, forming a silicon carbide film on a surface of the silicon carbide substrate ; in a second step, treating the surface of the silicon carbide film with predetermined ions so that a top doped region of the silicon carbide film close to a top surface of the silicon carbide film is doped with the predetermined ions, so as to increase concentration of the predetermined ions in the top doped region , the top doped region has a thickness of less than 10 nm, and the thickness of the top doped region is less than a thickness of the remaining portion of same silicon carbide film under the top doped region ; in a third step, forming another layer of silicon carbide film on the silicon carbide film ; and repeating the second and third steps at least once to successively form at least two layers of silicon carbide films which make up the buffer layer , wherein the silicon carbide substrate is successively subject to the first to third steps within the same process chamber, wherein the first step comprises forming the silicon carbide film by introducing a carbon-source gas and a silicon-source gas to the process chamber, and wherein the second step comprises stopping the introduction of the carbon-source gas and the silicon-source gas and then doping the top surface of the silicon carbide film by introducing a source of the predetermined ions to the process chamber, and wherein the third step comprises stopping the introduction of the source of the predetermined ions and then growing the other silicon carbide film by again introducing the silicon-source gas and the carbon-source gas. <EOS>