Abstract: A layout method of an analog/digital mixed semiconductor integrated circuit of the present invention has the steps of: quantitatively calculating a noise circulation amount with parameters of distances between an analog element, a digital element, and a substrate contact dedicated terminal for the digital element; calculating an optimal layout position of the substrate contact dedicated terminal from a position where the noise circulation amount is smallest; and placing the contact dedicated terminal in the optimal calculated layout position and in the layoutable position.

Abstract: A transient analysis device in which a simulation executing unit uses a first net list produced by a net list producing unit to measure a settling time of an analog/digital mixed circuit to be analyzed, after a dummy pulse parameter setting unit sets a parameter of a dummy pulse based on the measurement result, the net list producing unit converts, into a net list, a transfer function of a new circuit obtained as a result of the addition of a dummy pulse generation circuit for generating a dummy pulse whose parameter has been set to the analog/digital mixed circuit, and the simulation executing unit executes transient analysis processing by using a second net list produced with respect to the new circuit.