To increase the area of entire side wall face of a deep trench.

The method for making a deep trench comprises a first etching step for forming the tapered top part of a trench in a substrate by supplying plasma gas containing nitrogen fluoride, hydrogen bromide, and helium oxygen at a specified flow rate under a specified pressure, a second etching step for forming a bottle type bottom part in the trench by increasing the flow rate of hydrogen bromide and nitrogen fluoride thereby regulating the flow rate ratio of hydrogen bromide and helium oxygen at 4:1 or above, and a third etching step for keeping the bottle type profile 260 of the trench 261 through vertical etching by increasing the flow rate of hydrogen bromide and lowering the pressure. Since the bottle type profile 260 is obtained on the bottom of the trench 261 through the third etching step, width and depth of the deep trench are increased.