Three-layer light cover groove MOS device and manufacture method

The invention relates to a three-layer light cover groove MOS device and a manufacture method. After the manufacture of a groove and conductive polysilicon is completed, the invention uses different opening sizes of a grid electrode groove and a grid electrode contact groove, a groove opening of the grid electrode groove and a groove opening of the grid electrode groove have different shapes and appearances through the deposition of a dielectric layer with good step coverage capability, then, a dry method etching work procedure is carried out, a photoetching work procedure is carried out as the auxiliary, and the remaining of the dielectric layer in a required region can be realized. The remained dielectric layer can replace a photoresist mask film to be used as a mask film of N sourceelectrode ion injection and a mask film of P type trap ion injection, and the remained dielectric layer can also be used for self-aligning source electrode contact holes and self-aligning grid electrode contact holes. The inv