We present phase masks (PMs) made from birefringent CaCO3 crystal plates to create laser beams at an imaging plane with given shapes and intensity distributions close to flat-top distributions. The principle of PMs is based on creating the phase shift of π or 2π (depending on the initial plate thickness) in linearly polarized radiation passing through etched areas with given shapes. The phase shift in these areas is converted into the intensity distribution at an analyzer output, which can be projected with a demagnification by a high-quality lens into its imaging plane aligned with a microprocessing plane or target. In this research, we provide theoretical discussion of choosing PM configurations. PMs with the square and quadrating square shapes (such configurations are in demand in laser microprocessing and molecular optics) were fabricated by laser-induced microplasma and successfully tested in the experimental setup with a pulsed laser (with a wavelength of 1.06 μm and pulse duration of 120 ns). PMs were also used in this experimental setup for laser ablation of polished steel samples. Contours of footprints on samples were well matched with formed beam shapes.