The electrical machinery sensing element (1) the pressure chamber (21) and the ante-chamber (23) are formed by the baseplate (11), communicate the ante-chamber (23) with pressure chamber (21). The lower part electrode (33), the driver, the upper electrode (35) is formed with this order on the trailing membrane (13) which forms the wall surface (21a) of top of the pressure chamber (21) and the ante-chamber (23). The above-mentioned driver is located on the pressure chamber, (21) is smaller than cross section of the pressure chamber (21), it has possessed with the withdrawal section (31a) where aspect ratio of parallel direction to the surface of the baseplate (11) from the action department (31p) of abbreviation identical surface form and this action department (31p) is extended on the ante-chamber (23). The ante-chamber (23) 1st it lines up with the pressure chamber (21) direction crosses and at the same time balance to the surface of the baseplate (11) 2nd width of direction is smaller than the pressure chamber (21). In addition, as for the withdrawal section (31a) of the above-mentioned driver, description above 2nd width of direction is smaller than the ante-chamber (23).電気機械変換素子(1)の圧力室(21)および副室(23)は、基板(11)に形成されており、副室(23)は圧力室(21)と連通している。圧力室(21)及び副室(23)の上部の壁面(21a)をなす従動膜(13)の上には、下部電極(33)、駆動体、上部電極(35)がこの順で形成されている。上記駆動体は、圧力室(21)の上に位置し、圧力室(21)の断面形状よりも小さく、基板(11)の面に平行な方向の縦横比が略同一の面形状の作用部(31p)と、この作用部(31p)から副室(23)の上に延長された引出部(31a)とを有している。副室(23)は、圧力室(21)と並ぶ第1の方向と直交し且つ基板(11)の面に平行な第2の方向の幅が圧力室(21)よりも小さい。また、上記駆動体の引出部(31a)は、上記第2の方向の幅が副室(23)よりも小さい。
