A method of manufacturing a solid-state image sensor is provided. The method comprises: depositing a gate electrode film above the semiconductor layer; etching the gate electrode film to form a first gate electrode patterned in a pixel region, leaving the gate electrode film in a peripheral region; depositing a first insulating film above the semiconductor layer after the forming the first gate electrode; removing the first insulating film formed in the peripheral region; etching the gate electrode film left in the peripheral region to form a second gate electrode patterned in the peripheral region after the removing the first insulating film; forming a second insulating film above the semiconductor layer after the forming the second gate electrode; and forming a side wall on side surface of the second gate electrode by etching the second insulating film.