The micro-fabrication technology requires high force, high displacement, low mass actuators low step frequencies, high power and energy density. Upon this point, piezoelectric transformer (PT) are promising and have some advantages compared with the usual electromagnetic ones operating at resonance. Besides, their electromechanical behaviors depend several parameters such as the operating frequency, load located to the output electrodes as well as the gap. Recently, for a transverse-type PT, Hamilton’s principle or the equivalent circuit model have been used but the gap (distance between the primary and secondary electrodes) is neglected. Now, the polynomial approach (PA) which a semi-analytical method is applied in this manuscript to develop and illustrate the 2D modeling of this type PT taking into account the gap.