We have demonstrated corrugated horn antennas at 560 GHz fabricated with a deep reactive ion etching (DRIE) process on silicon. The measurement of two of the ( 2 times 2)560 GHz array antenna has shown that the return loss and directivity are 13 dB and 22 dB, respectively. All of the measured antennas had below-25 dB of the cross-polarization and symmetrical beam patterns. The silicon microfabrication technique enables us to build hundreds of horn antennas at once, allowing construction of multi-pixel heterodyne imagers and spectrometers at submillimeter wavelengths.