Manufacturing method of image sensor

The invention provides a manufacturing method of an image sensor, which is applied to the technical field of semiconductors. Specifically, after a first deep well region and a second deep well region are formed by an existing method, photoresist layers forming the first deep well region and the second deep well region are not removed; a dielectric layer (a first dielectric layer or a second dielectric layer) which can be subjected to chemical mixing reaction with chemical bonds of the photoresist layer is further formed on the photoresist layer, and then the dielectric layer and the photoresist layer are subjected to chemical reaction, so that the photoresist layer with the changed size is obtained; and the photoresist layer is used as a photoresist layer for forming the third deep well region and the fourth deep well region, so that a photoetching process for forming the third deep well region and the fourth deep well region in the prior art is omitted, a photomask is saved, and the productivity of a scanner