Tunneling (one-particle excitation) density of states in the vicinity of Fermi level of a two-dimensional electron gas (2DEG) subjected to an external parallel and zero magnetic field is calculated. It reveals a pseudo-gap recently observed in the experiments. The gap originates in spin polarization of 2DEG. Nonmonotonic dependence of energy on a Landau level filling factor (density) for perpendicular magnetic field was also obtained. It implies the tunneling current peculiarities at filling factors of about 1/2 and 1. The Ising-like model of the exchange interaction in 2DEG was exploited instead of the conventional one. It was crucial to achieve even a qualitative agreement with experimental data.