To provide a method for manufacturing a semiconductor device, which can prevent an increase in the number of processes, deterioration in quality and an increase in a chip size while improving the mobility of a carrier in a channel of a transistor.

A compressive nitride film 13 for inducing compressive stress to a channel of a PMOS transistor 2 is formed on a Si substrate 1. Then, the compressive nitride film 13 formed in an NMOS region 5 is etched by using first mixed gas obtained by mixing fluorine-based gas and O2 gas. Then, a tensile nitride film 15 for inducing tensile stress to a channel of an NMOS transistor 3 is formed on the compressive nitride film 13 in the PMOS region 4 and on the Si substrate 1 in the NMOS region 5. The tensile nitride film 15 formed in the PMOS region 4 is etched selectively for the compressive nitride film 13 by using second mixed gas obtained by mixing the fluorine-based gas and the O2 gas. Wherein, the O2 partial pressure of the second mixed gas is set lower than that of the first gas.