The research of optimal condition for etching silicon in TMAH solution with controlled etch rate and low surface roughness is the purpose of this study. The investigation on the influence of temperature, agitation, size of etch-window, etch time on etch rate and the surface roughness were carried out. With the TMAH concentration of 20% in weight, the optimal etching conditions were as follows: temperature of about 80 – 90 oC, agitation of 150 - 200 rpm. The etch rate is controlled in range of 0.49 – 0.72 $\mu$m/min. The etched surface roughness was lower than 70 nm. Development of TMAH application, a useful procedure for fabricating MEMS structures (piezoresistive accelerometer) was suggested.
