A probe card for wafer level testing of a plurality of semiconductor devices simultaneously. The probe card may include a circuit board including wafer level testing circuitry, a partially flexible silicon substrate, a plurality of test probes disposed at least partially in the substrate for engaging a plurality of corresponding electrical contacts in a wafer under test, and a compressible underfill coupling the substrate to the circuit board. The probe card may be used for wafer level burn-in testing. In some embodiments, the probe card may include active test control circuitry embedded in the silicon substrate for conducting wafer level high frequency testing.