As silicon has a large refractive index and low loss in infrared wavelengths, it becomes an important optical material that has been widely used for integrated photonics applications. Some of our recent research progress on infrared two-dimensional silicon photonic crystal slab devices are presented. A series of photonic crystal waveguides are fabricated and characterized with novel geometries, resonant microcavities with fine tunability, and channel drop filters utilizing resonant coupling between waveguide and cavity. The remarkable dispersion properties of photonic crystals are also explored by engineering the band structures to achieve negative refraction and self-collimation effects of infrared light beams. The progress towards building and characterizing high-Q photonic crystal cavities is further introduced. All these results show that silicon photonic crystal can control light propagation in many flexible ways and have many potential applications in all-optical integrated circuits.