Improvement of THz waveguides with reduced losses has seen a rapid progress in the recent years. Among designs with the low loss, Planar Goubau Line have been designed and fabricated on high resistivity silicon substrate. In this contribution, we discuss two kinds of Planar Goubau lines: rectangular cross section line for low loss transmission and corrugated line in order to slow down and confine the electromagnetic waves. Moreover, in this paper we present our low-loss waveguides and focus mainly on the influence of strip width and the length of the PGL on the S-parameters. The measured loss at 210 GHz is 2.5 dB. This value of loss could be tuned depending on certain parameters such as length, width of the rectangular cross section, the dimension of the coplanar waveguide transition or the thickness of the silicon substrate, etc. At the end of this communication, we show an example of the corrugated PGL that could be used first to confine and to slow down the electromagnetic propagation, and second to be a candidate for a filter application in the THz domain.