Provided herein is a method for manufacturing a semiconductor device. A substrate including a MEMS region and a connection region thereon is provided; a dielectric layer disposed on the substrate in the connection region is provided; a poly-silicon layer disposed on the dielectric layer is provided, wherein the poly-silicon layer serves as an etch-stop layer; a connection pad disposed on the poly-silicon layer is provided; and a passivation layer covering the dielectric layer is provided, wherein the passivation layer includes an opening that exposes the connection pad and a transition region between the connection pad and the passivation layer, and a conductive layer conformally covering the connection pad and the poly-silicon layer in the transition region is provided.