In this paper, we present a simple method for electropolymerization process that combines aniline–silane (C6H5NHC3H6Si(OMe)3) surface modified indium-tin-oxide (ITO) to prepare thin, polyaniline (PANI) films with good surface coverage. The modified surface enhances the growth of PANI film resulting in a smoother surface, dense, strongly adhered film, higher electropolymerization activity and stability than those deposited on unmodified ITO substrates. PANI film deposited on modified ITO substrate was used as a modified base terminal in a metal-base-transistor (MBT), which used tris(8-hydroxyquinoline) aluminum (Alq3) as an emitter layer, LiF as a buffer layer, and Al as a cathode. The MBT, tested at in ambient atmosphere, and without the presence of magnetic-field, has a comparable but stable current gain, 6.5 than that of a device with a sulfonated polyaniline (SPANI) based metal-base transistor. With this simple and easy electropolymerization method, the on-to-off current ratio achieved 6.9×104.