Method of manufacturing an image sensor and image sensor

A method of manufacturing a back-side (14) illuminated image sensor (1) is disclosed, comprising the steps of: starting with a wafer (2) having a first (3) and a second surface (4), providing light sensitive pixel regions (5) extending into the wafer (2) from the first surface (3), securing the wafer (2) onto a protective substrate (7) such that the first surface (3) faces the protective substrate, the wafer comprising a substrate of a first material (8) with an optical transparant layer (9) and a layer of semiconductor material (10), wherein the substrate (8) is selectively removed from the layer of semiconductor material by using the optical transparant layer (9) as stopping layer. For back-side illuminated image sensors, light has to transmit through the semiconductor layer and enter into the light sensitive pixel regions (5). In order to reduce absorption losses, it is very advantageous that the semiconductor layer (10) can be made relatively thin with a good uniformity. Because of the reduced thickness of the semiconductor layer, more light can enter into the light sensitive regions, resulting in an improved efficiency of the image sensor.