Method of manufacturing silicon carbide semiconductor substrate and method of manufacturing silicon carbide semiconductor device

A method of manufacturing a silicon carbide semiconductor substrate, comprising steps of:

• preparing a silicon carbide substrate;
• forming a first silicon carbide semiconductor layer on the silicon carbide substrate using a first source material gas;
• and
• forming a second silicon carbide semiconductor layer on the first silicon carbide semiconductor layer using a second source material gas,
• in the step of forming a first silicon carbide semiconductor layer and the step of forming a second silicon carbide semiconductor layer, ammonia gas being used as a dopant gas, the first source material gas having a C/Si ratio of not less than 1.6 and not more than 2.2, the C/Si ratio being the number of carbon atoms to the number of silicon atoms,
• a flow rate of the first source material gas being different from a flow rate of the second source material gas.