Manufacturing method of semiconductor device and semiconductor manufacturing apparatus

An etching apparatus includes a process unit and a control unit. Emission intensity of plasma inside the process unit is obtained by an OES detector, a nonlinear regression analysis is performed by an etching control device to determine a regression formula. The nonlinear regression analysis is performed by using the emission intensity of the plasma obtained until a first time when the emission intensity of the plasma passes a peak, and a second time to be an etching end point is calculated by using the regression formula. The etching end point is calculated as a time when the emission intensity decreases for a predetermined value from the first time. The etching apparatus finishes an etching when the process reaches the etching end point. It is thereby possible to control the etching end point with high-accuracy.