US Patent 7589012 Method for fabricating semiconductor memory device

Disclosed herein is a method for fabricating a semiconductor memory device that can prevent oxidation of bit lines when forming an interlayer dielectric for isolating the bit lines. The bit line is formed on a semiconductor substrate where an underlying structure is formed. A silicon on dielectric (SOD) layer is formed on the resulting structure where the bit line is formed. A heat treatment can be performed on the SOD layer with a partial pressure ratio of water vapor (H2O) to hydrogen (H2) in a range of about 1×10−11 to about 1.55 at a temperature in a range of about 600° C. to about 1,100° C.