A method of manufacturing a packaged semiconductor device, the method comprising the steps of: encapsulating a semiconductor die in encapsulant material, wherein the semiconductor die has a top die surface, a bottom die surface, and a first conductive feature (106, 506) coupled to the bottom die surface, wherein the first conductive feature (106, 506) only partially covers the bottom die surface to define a first conductor-less region (580, 582, 584, 586) that spans a first portion of the bottom die surface, the semiconductor die includes: a transistor (120, 420), wherein a first current conducting terminal of the transistor (120, 420) is electrically coupled to the first conductive feature, and a first filter circuit (110, 120, 210, 230, 310, 330) electrically coupled to the transistor (120, 420), wherein the first filter circuit (110, 120, 210, 230, 310, 330) includes a passive component (214, 215, 232, 234) formed in a portion of the semiconductor die that is directly opposite the first conductor-less region (580, 582, 584, 586), and wherein the passive component (214, 215, 232, 234) is selected from an inductor and a capacitor and wherein encapsulating the semiconductor die includes attaching encapsulant material to the bottom die surface over the first conductor-less region (580, 582, 584, 586), wherein the encapsulant material includes a first opening (1610, 2110) that exposes the first conductive feature (106, 506), and wherein the first opening (1610, 2110) has encapsulant sidewalls (1612, 2112) extending from an outer surface of the encapsulant material toward the bottom die surface; after encapsulating the semiconductor die, positioning a heatsink (1810, 1910) within the first opening (1610, 2110), wherein the heatsink (1810, 1910) has a first heatsink surface (1812, 1912), a second heatsink surface, and heatsink sidewalls (1816, 1916, 2316) extending between the first and second heatsink surfaces (1812, 1912, 1824); and attaching the first heatsink surface (1812, 1912) to the first conductive feature (106, 506). a transistor (120, 420), wherein a first current conducting terminal of the transistor (120, 420) is electrically coupled to the first conductive feature, and a first filter circuit (110, 120, 210, 230, 310, 330) electrically coupled to the transistor (120, 420), wherein the first filter circuit (110, 120, 210, 230, 310, 330) includes a passive component (214, 215, 232, 234) formed in a portion of the semiconductor die that is directly opposite the first conductor-less region (580, 582, 584, 586), and wherein the passive component (214, 215, 232, 234) is selected from an inductor and a capacitor and wherein encapsulating the semiconductor die includes attaching encapsulant material to the bottom die surface over the first conductor-less region (580, 582, 584, 586), wherein the encapsulant material includes a first opening (1610, 2110) that exposes the first conductive feature (106, 506), and wherein the first opening (1610, 2110) has encapsulant sidewalls (1612, 2112) extending from an outer surface of the encapsulant material toward the bottom die surface; after encapsulating the semiconductor die, positioning a heatsink (1810, 1910) within the first opening (1610, 2110), wherein the heatsink (1810, 1910) has a first heatsink surface (1812, 1912), a second heatsink surface, and heatsink sidewalls (1816, 1916, 2316) extending between the first and second heatsink surfaces (1812, 1912, 1824); and attaching the first heatsink surface (1812, 1912) to the first conductive feature (106, 506).