Silicon is an excellent material for sensing. Sensors for all signal domains can be realised, and in many cases, integrated with read-out electronics. However, in some applications an addition layer may be required for sensing and/or to protect the silicon device. Piezoelectric, polymers or magneto resistive layers can be added to expand the options of silicon. In the case of some implants, the polymer is used to protect the body from the device. In harsh chemical environments, the coating layer can be used to protect the silicon and in some cases also function as the sensor. Layers such as SiC represent a chemically resilient layer to protect the layers below, but this layer can also be used as a sensing layer. Atomic layer deposition (ALD) provides thin uniform, and pinhole free layers which can be used as protection and sensing. Other materials include graphene. In cases such as extreme temperature, it is more difficult to protect the silicon device, and in these cases the electronics must be isolated from the heat. This paper will show examples of how coating layers can enhance the sensing capabilities of silicon devices and also provide protection.