We report on room temperature current voltage characteristics of epitaxially grown Si/SiGe/Si p(+)/i/n(+) tunneling diodes based on Si substrate. The structures are prepared by solid source MBE. Very sharp and high p- and n-type doping into the 10(20) cm(-3) range is achieved bq boron and phosphorous using Gap as source material, respectively. Extremely high peak current densities (PCD) up to 30 kA cm(-2) and record peal, to valley current ratios (PVCR) of more than 6 are measured at room temperature. These values together with intrinsic peak voltages of about V-p = 0.1 V, valley voltages of V-v = 0.4 V and a voltage swing of V-s = 0.8 V fulfill the requirements for typical digital circuit applications. In the second type of interband tunneling diodes we prepared Si n(+)/p(+)/n(+) structures. First results indicate a room temperature PVCR up to 2. In the second part we present a new concept for resonant p/i/p intraband tunneling diodes based on self-assembled Ge islands. The structure consists of closely stacked and vertically aligned Ge islands formed by Stranski Krastanov growth. The aligned Ge islands create vertical channels with energetically deep thermalization layers and high Si double barriers for holes in the valence band. Ge islands provide access to larger band offsets as compared to formerly investigated tunneling structures with planar pseudomorphic SiGe quantum well layers. First measurements of I-V characteristics show two resonances which are attributed to heavy-heavy hole (hh) and heavy-light hole (Ih) transitions. The lh resonance shows negative differential resistance up to temperatures above 50 K.