In this work, a theoretical model of the surface plasma oscillations' propagation in a conductive layer is constructed. We assume that the layer is located between two insulating layers with the same dielectric constants. We suppose that the surface wave frequency is much lower than the plasma resonance frequency. The case of specular reflection of charge carriers from the semiconductor layer boundaries is considered. Analytical expressions for the propagation coefficients, longitudinal, and transverse attenuation parameters are derived. An analysis of the dependencies of the surface wave parameters on the semiconductor layer thickness, surface wave frequency, and the dielectric constant of insulating layers was carried out. We established that at low frequencies (about ten THz), we observe a linear frequency dependence of the surface wave propagation coefficient. The longitudinal attenuation is practically absent, which may be due to the absence of excess charge at the layer boundaries. At a certain frequency, the longitudinal attenuation coefficient becomes non-zero, and it grows sharply with increasing frequency. The appearance of non-zero longitudinal attenuation is accompanied by a deviation of the frequency propagation coefficient dependence from the linear law. With a further increasing frequency, the propagation and attenuation parameters grow, reach a maximum, and then reduce. It follows from the above that when a non-monochromatic wave arrives at the conductive layer, a redistribution of harmonics across amplitudes occurs during surface wave propagation. This effect can be used to create plasmonic waveguides that filter frequencies corresponding to the minimum longitudinal attenuation coefficient (plasmonic filters). We established that with rising semiconductor layer thickness and dielectric constant of insulating layers, the propagation and attenuation parameter maxima shift towards lower frequencies. Thus, by varying the thickness and selecting the material of the insulating layers with the desired optical characteristics, it is possible to change plasmonic filter pass frequency.