A die includes: a semiconductor substrate; an interconnect structure disposed on the semiconductor substrate and including: inter-metal dielectric (IMD) layers; metal features embedded in the IMD layers; and a guard ring structure including concentric first and second guard rings that extend through at least a subset of the IMD layers; and a through silicon via (TSV) structure extending through the semiconductor substrate and the subset of IMD layers to electrically contact one of the metal features. The first guard ring surrounds the TSV structure; and the second guard ring surrounds the first guard ring and is configured to reduce a parasitic capacitance between the guard ring structure and the TSV structure.