This study optimizes Si1-xGex based double gate tunnel field effect transistor (TFET) for their high ON current (Ion) and lesser sub-threshold swing and compares Si and Si1-xGex based single material double gate (SMDG) and dual material double gate (DMDG) TFETs. This study also measures the two RF performance metrics, unity gain cut-off frequency ( ft) and maximum oscillation frequency ( fmax) by varying the structural parameters, gate length, gate oxide thickness, channel thickness and underlap. Compared to single material gate devices, dual material gate devices give higher Ion without compromising the leakage current for both Si and Si1-xGex based TFETs. Si1-xGex based TFETs offers higher ft and fmax compared to that of Si TFETs for all the structural parameter variations considered in this study. DMDG TFETs exhibit higher ft with respect to SMDG TFETs. SMDG TFETs offers more fmax compared to DMDG TFETs due to the smaller values of output conductance. © 2016 Vietnam Academy of Science & Technology.