There is provided an imaging device manufacturing method contributing to improved reliability and yield. The method includes forming a first insulating film on a polysilicon film and then removing a portion of the first insulating film formed on a second main surface and a portion of the first insulating film formed on a side surface of the substrate to expose a polysilicon film. After the polysilicon film is exposed, a second insulating film is formed on the first main surface by a plasma chemical vapor deposition (CVD) method.