Method for etching silicon layer and plasma processing apparatus

A method of etching a silicon layer of an object to be processed (“workpiece”), the method comprising:

• forming a denatured region by generating plasma of a first processing gas containing hydrogen, nitrogen, and fluorine within a processing container accommodating the workpiece therein to denature an oxide film formed on a surface of the workpiece including a mask provided on the silicon layer;
• removing the denatured region by generating plasma of a second processing gas within the processing container following to forming the denatured region without taking out the workpiece from the processing container;
• and
• etching the silicon layer by generating plasma of the second processing gas within the processing container.