The Structure Functions F_2^c, F_L and F_L^c in the Framework of the k_T Factorization

We present the perturbative parts of the structure functions F_2^c and F_L^c for a gluon target having nonzero transverse momentum squared at order alpha _s. The results of the double convolution (with respect to the Bjorken variable x and the transverse momentum) of the perturbative part and the unintegrated gluon densities are compared with HERA experimental data for F_2^c and F_L at low x values and with predictions of other approaches. The contribution from F_L^c structure function ranges 10div30% of that of F_2^c at the HERA kinematical range.