By using a cw $Ar^+$ ion laser beam, microscopic crystalline silicon rods ~$10^2㎛$ in diameter and ~$10^3㎛$ in height have been grown on a silicon substrates by pyrolytic dissociation of $SiH_4$. The kinesics of lateral growth of the silicon rods is derived from the time integration of the Arrhenius equation using a reasonable assumption that the temperature on the edge of the deposit saturates inversely to the substrate temperature with illumination time. For the axial growth, excluding the initial transient growth the same result as B$\ddot{a}$uerle and his collaborators is derived. The influences of laser power and illumination time on the deposited diameter and height are found experimentally and it is found that the derived theory agrees well with the experimental results.
