CMUT (capacitive micromachined ultrasonic transducer) patents typically claim electrostatic membrane actuation, bias-voltage schemes and collapse-mode operation, while PMUT (piezoelectric micromachined ultrasonic transducer) patents claim piezoelectric thin-film actuation on a MEMS membrane. Both are captured in this 284-record dataset because the search targets either term appearing in the title alongside fabrication and performance language. In practice, the IPC mix shows heavy overlap in B06B and H10N classes, meaning many filings claim structural or fabrication features common to both approaches rather than being purely CMUT- or PMUT-specific.

The ranking covers 57 companies, with the leading assignee holding 33 records against 16 for the fifth-place filer — a meaningful gap that marks genuine leadership. The top five combined account for 43.7% of all 284 records, and the top ten reach 66.5%, so activity is concentrated but far from a duopoly. Beyond the leading group, filing counts drop quickly into single digits across a long tail of academic and corporate entrants.

Filings peaked at 25 in 2021 and fell to 12 by 2024, a -52% change over that span, which reads as a genuine pullback from an earlier filing wave. However, publication typically lags filing by around 18 months, so figures for 2025 and 2026 are still incomplete and should not be read as confirmation of further decline. The safest read is that the first wave of core fabrication patents matured around 2021 and later activity has shifted toward narrower, more specific claims.