Method for fabricating semiconductor device

According to the present invention, a method for fabricating a semiconductor device includes the steps of: providing a semiconductor substrate; providing a diffusion layer in the semiconductor substrate; providing a first oxide layer on the semiconductor substrate; providing a poly-silicon layer on the first oxide layer; introducing phosphorus into the poly-silicon layer; selectively removing the poly-silicon layer to form a conductive pattern; removing the first oxide layer from the semiconductor substrate; and performing a cleaning process within approximately two hours since the first oxide layer is removed.