A method of forming a semiconductor device includes the following operations. A substrate is provided with a device and an insulating layer disposed over the device. A silicon-containing heterocyclic compound precursor and a first oxygen-containing compound precursor are introduced to the substrate, so as to form a zeroth dielectric layer on the insulating layer. A zeroth metal layer is formed in the zeroth dielectric layer. A silicon-containing linear compound precursor and a second oxygen-containing compound precursor are introduced to the substrate to form a first dielectric layer on the zeroth dielectric layer. A first metal layer is formed in the first dielectric layer.