In this paper we describe the evaluation of the dependence of low frequency noise upon the micro‐roughness of the surface in pMOSFETs, based on (100) and (110) oriented silicon. For the (110) surface, because RCA cleaning makes the surface rough, we developed a 5 step room temperature cleaning process which does not use alkaline solution. As a result a drop of more than a decade in 1/f noise level was achieved. This low noise level is further reduced by using the process of microwave‐excited high‐density plasma oxidation of the gate oxide instead of thermal oxidation. This reduction is also observed for a (100) surface if treated in the same way, but the magnitude of the drop is less.