By a non-selective epitaxial growth method, an SiGe film is grown on the whole
surface of a silicon oxide film so as to cover an inner wall of a base opening.
Here, such film forming conditions are selected that, inside the base opening,
a bottom portion is formed of single crystal, other portions such as a sidewall
portion are formed of polycrystalline, and a film thickness of the sidewall portion
is less than or equal to 1.5 times the film thickness of the bottom portion. In
this nonselective epitaxial growth, monosilane, hydrogen, diborane, and germane
are used as source gases. Then, flow rates of monosilane and hydrogen are set to
20 sccm and 20 slm respectively. Also, a growth temperature is set to 650
C., a flow rate of diborane is set to 75 sccm, and a flow rate of germane is set
to 35 sccm.
