  We investigate the surface roughness influence on the gain from parametric
amplification in nanoresonators in presence of thermomechanical and momentum
exchange noise. The roughness is characterized by the rms amplitude w, the
correlation length X, and the roughness exponent 0<H<1. It is found that the
gain strongly increases with increasing roughening (decreasing H and/or
increasing ratio w/ X) due to increment of capacitive coupling, which plays
dominant role when the intrinsic quality factor Qin is comparable or lower than
the quality factor Qgas due to gas collisions. However, for Qin>>Qgas, the
influence of surface roughness on the gain strongly diminishes.
