To use pure water for preventing the entry of dust to a small gap by absorbing and reducing pressure being applied to a fragile part in inertial sensor chip semi-finished goods caused by accumulated inflation and preventing the damage.

Semi-finished goods are provided with a single silicon substrate or a mass part formation substrate 1 where a number of inertia sensor mass parts 11 are formed in a matrix by applying a melted crystal substrate bulk micro-machining manufacturing technology and is composed by sandwiching the mass part formation substrate 1 between an upper support substrate 2 and a lower support substrate 3 and joining the three in one piece. In this case, diaphragm parts 21 and 31 are formed at one or both of the upper support substrate 2 and the lower support substrate 3.