A three-dimensional multispectral imaging sensor and method for forming a three-dimensional multispectral imaging sensor are provided. The three-dimensional multispectral imaging sensor includes a monolithic structure having a plurality of layers. Each of the layers is formed from light detecting materials for detecting light of respective different non-overlapping wavelengths and having respective different bandgaps

An imaging device with excellent imaging performance is provided. An imaging device that easily performs imaging under a low illuminance condition is provided. A low power consumption imaging device is provided. An imaging device with small variations in characteristics between its pixels is provided. A highly integrated imaging device is provided. A photoelectric conversion element includes a first electrode, and a first layer, a second layer, and a third layer. The first layer is provided between the first electrode and the third layer. The second layer is provided between the first layer and the third layer. The first layer contains selenium. The second layer contains a metal oxide. The third layer contains a metal oxide and also contains at least one of a rare gas atom, phosphorus, and boron. The selenium may be crystalline selenium. The second layer may be a layer of an InGaZn oxide including c-axis-aligned crystals.