To conduct highly selective etching even at low gas pressure by a method wherein the rise in temperature of the electron in plasma is suppressed, using an etching gas which contains chlorine-containing gas and fluorine- containing gas.

A compound semiconductor substrate 16 is placed on a holder 14 using an inductively coupled device 10, for example, as a low voltage and high density plasma etching device. Then, an etching chamber 12 is evacuated. Next, SiCl4 gas and SF6 gas are introduced into the etching chamber, for example at a flow rate ratio of 1:4 the speed of evacuation of the etching chamber is adjusted, and gas pressure is adjusted to 0.1 Pa. Subsequently, since electricity is discharged by supplying power to accelerate discharge to a pulse-modulated antenna 18, the temperature of electrons drops when an applied voltage is turned off intermittently, and the electron temperature can be suppressed low. A compound semiconductor can be etched with high selectivity even at a low gas pressure, because the compound semiconductor layer is etched, while its temperature rise is being suppressed using pulse modulated plasma.