Semiconductor device preparation method and semiconductor device

The invention discloses a semiconductor device preparation method and a semiconductor device, and the method comprises the steps of forming a conductive stacking layer on a substrate, depositing a first insulating dielectric layer covering the conductive stacking layer at a first temperature, and patterning the first insulating dielectric layer and the conductive stacking layer of a peripheral circuit region of the substrate, so as to form a gate structure; performing heat treatment on the first insulating dielectric layer, the conductive stacking layer, the gate structure and the substrate; depositing a second insulating dielectric layer at a second temperature higher than the first temperature, enabling the second insulating dielectric layer to at least cover the first insulating dielectric layer located in the unit array region, patterning the first insulating dielectric layer and the second insulating dielectric layer in the unit array region; taking the patterned first insulatingdielectric layer and the