EXHIBIT 12.1**CERTIFICATION OF CHIEF EXECUTIVE OFFICER**I, Dr. Wolfgang Ziebart, certify that:1. I have reviewed this annual report on Form 20-F, as amendedby Amendment No. 1 and No. 2 thereto, ofInfineon Technologies AG; 2. Based on my knowledge, this annual report does not contain any untrue statement of a materialfact or omit to state a material fact necessary to make the statements made, in light of thecircumstances under which such statements were made, not misleading with respect to the periodcovered by this annual report; 3. Based on my knowledge, the financial statements, and other financial information included inthis annual report, fairly present in all material respects the financial condition, resultsof operations and cash flows of the registrant as of, and for, the periods presented in thisannual report; 4. The company’s other certifying officer and I are responsible for establishing and maintainingdisclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e))and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and15d-15(f)) for the company and have: (a) designed such disclosure controls and procedures, or caused such disclosurecontrols and procedures to be designed under our supervision, to ensure that materialinformation relating to the company, including its consolidated subsidiaries, is madeknown to us by others within those entities, particularly during the period duringwhich this annual report is being prepared;  (b) designed such internal control over financial reporting, or caused suchinternal control over financial reporting to be designed under our supervision, toprovide reasonable assurance regarding the reliability of financial reporting and thepreparation of financial statements for external purposes in accordance with generallyaccepted accounting principles;  (c) evaluated the effectiveness of the company’s disclosure controls and proceduresand presented in this annual report our conclusions about the effectiveness of thedisclosure controls and procedures, as of the end of the period covered by this annualreport based on such evaluation; and  (d) disclosed in this annual report any change in the company’s internal controlover financial reporting that occurred during the period covered by this annual reportthat has materially affected, or is reasonably likely to materially affect, thecompany’s internal control over financial reporting.5. The company’s other certifying officer and I have disclosed, based on our most recentevaluation of internal control over financial reporting, to the company’s auditors and theaudit committee of the company’s board of directors (or persons performing the equivalentfunctions): (a) all significant deficiencies and material weaknesses in the design or operationof internal controls over financial reporting which are reasonably likely to adverselyaffect the company’s ability to record, process, summarize and report financialinformation; and  (b) any fraud, whether or not material, that involves management or other employeeswho have a significant role in the company’s internal controls over financialreporting.Date: April 17, 2008         /s/  Wolfgang Ziebart   Dr. Wolfgang Ziebart   Member of the Management Boardand